{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "<p align=\"center\"><img src=\"/images/logo.png\" alt=\"\"></p>\n",
        "<h1 align=\"center\">What the f*ck Python! \ud83d\udc0d</h1>\n",
        "<p align=\"center\">\u4e00\u4e9b\u6709\u8da3\u4e14\u9c9c\u4e3a\u4eba\u77e5\u7684 Python \u7279\u6027.</p>\n",
        "\n",
        "\u7ffb\u8bd1\u7248\u672c: [English](https://github.com/satwikkansal/wtfpython) | [Vietnamese Ti\u1ebfng Vi\u1ec7t](https://github.com/vuduclyunitn/wtfptyhon-vi) | [Spanish Espa\u00f1ol](https://web.archive.org/web/20220511161045/https://github.com/JoseDeFreitas/wtfpython-es) | [Korean \ud55c\uad6d\uc5b4](https://github.com/buttercrab/wtfpython-ko) | [Russian \u0420\u0443\u0441\u0441\u043a\u0438\u0439](https://github.com/frontdevops/wtfpython) | [Add translation](https://github.com/satwikkansal/wtfpython/issues/new?title=Add%20translation%20for%20[LANGUAGE]&body=Expected%20time%20to%20finish:%20[X]%20weeks.%20I%27ll%20start%20working%20on%20it%20from%20[Y].)\n",
        "\n",
        "\n",
        "\u5176\u4ed6\u6a21\u5f0f: [Interactive](https://mybinder.org/v2/gh/robertparley/wtfpython-cn/master?labpath=irrelevant%2Fwtf.ipynb) \n",
        "\n",
        "\n",
        "[![WTFPL 2.0][license-image]][license-url] [![Commit id][commit-image]][commit-url] [![996.icu][996.icu-image]][996.icu-url]\n",
        "\n",
        "\n",
        "Python, \u662f\u4e00\u4e2a\u8bbe\u8ba1\u4f18\u7f8e\u7684\u89e3\u91ca\u578b\u9ad8\u7ea7\u8bed\u8a00, \u5b83\u63d0\u4f9b\u4e86\u5f88\u591a\u80fd\u8ba9\u7a0b\u5e8f\u5458\u611f\u5230\u8212\u9002\u7684\u529f\u80fd\u7279\u6027. \u4f46\u6709\u7684\u65f6\u5019, Python \u7684\u4e00\u4e9b\u8f93\u51fa\u7ed3\u679c\u5bf9\u4e8e\u521d\u5b66\u8005\u6765\u8bf4\u4f3c\u4e4e\u5e76\u4e0d\u662f\u90a3\u4e48\u4e00\u76ee\u4e86\u7136.\n",
        "\n",
        "\u8fd9\u4e2a\u6709\u8da3\u7684\u9879\u76ee\u610f\u5728\u6536\u96c6 Python \u4e2d\u90a3\u4e9b\u96be\u4ee5\u7406\u89e3\u548c\u53cd\u4eba\u7c7b\u76f4\u89c9\u7684\u4f8b\u5b50\u4ee5\u53ca\u9c9c\u4e3a\u4eba\u77e5\u7684\u529f\u80fd\u7279\u6027, \u5e76\u5c1d\u8bd5\u8ba8\u8bba\u8fd9\u4e9b\u73b0\u8c61\u80cc\u540e\u771f\u6b63\u7684\u539f\u7406!\n",
        "\n",
        "\u867d\u7136\u4e0b\u9762\u7684\u6709\u4e9b\u4f8b\u5b50\u5e76\u4e0d\u4e00\u5b9a\u4f1a\u8ba9\u4f60\u89c9\u5f97 WTFs, \u4f46\u5b83\u4eec\u4f9d\u7136\u6709\u53ef\u80fd\u4f1a\u544a\u8bc9\u4f60\u4e00\u4e9b\u4f60\u6240\u4e0d\u77e5\u9053\u7684 Python \u6709\u8da3\u7279\u6027.  \u6211\u89c9\u5f97\u8fd9\u662f\u4e00\u79cd\u5b66\u4e60\u7f16\u7a0b\u8bed\u8a00\u5185\u90e8\u539f\u7406\u7684\u597d\u529e\u6cd5, \u800c\u4e14\u6211\u76f8\u4fe1\u4f60\u4e5f\u4f1a\u4ece\u4e2d\u83b7\u5f97\u4e50\u8da3!\n",
        "\n",
        "\u5982\u679c\u60a8\u662f\u4e00\u4f4d\u7ecf\u9a8c\u6bd4\u8f83\u4e30\u5bcc\u7684 Python \u7a0b\u5e8f\u5458, \u4f60\u53ef\u4ee5\u5c1d\u8bd5\u6311\u6218\u770b\u662f\u5426\u80fd\u4e00\u6b21\u5c31\u627e\u5230\u4f8b\u5b50\u7684\u6b63\u786e\u7b54\u6848. \u4f60\u53ef\u80fd\u5bf9\u5176\u4e2d\u7684\u4e00\u4e9b\u4f8b\u5b50\u5df2\u7ecf\u6bd4\u8f83\u719f\u6089\u4e86, \u90a3\u8fd9\u4e5f\u8bb8\u80fd\u5524\u8d77\u4f60\u5f53\u5e74\u8e29\u8fd9\u4e9b\u5751\u65f6\u7684\u751c\u871c\u56de\u5fc6 :sweat_smile:\n",
        "\n",
        "PS: \u5982\u679c\u4f60\u4e0d\u662f\u7b2c\u4e00\u6b21\u8bfb\u4e86, \u4f60\u53ef\u4ee5\u5728[\u8fd9\u91cc](https://github.com/satwikkansal/wtfpython/releases/)\u83b7\u53d6\u53d8\u52a8\u5185\u5bb9.\n",
        "\n",
        "\u90a3\u4e48, \u8ba9\u6211\u4eec\u5f00\u59cb\u5427...\n",
        "\n",
        "# Table of Contents/\u76ee\u5f55\n",
        "<!-- TOC -->\n",
        "\n",
        "- [Table of Contents/\u76ee\u5f55](#table-of-contents\u76ee\u5f55)\n",
        "- [Structure of the Examples/\u793a\u4f8b\u7ed3\u6784](#structure-of-the-examples\u793a\u4f8b\u7ed3\u6784)\n",
        "- [Usage/\u7528\u6cd5](#usage\u7528\u6cd5)\n",
        "- [\ud83d\udc40 Examples/\u793a\u4f8b](#-examples\u793a\u4f8b)\n",
        "    - [Section: Strain your brain!/\u5927\u8111\u8fd0\u52a8!](#section-strain-your-brain\u5927\u8111\u8fd0\u52a8)\n",
        "        - [> First things first!/\u8981\u4e8b\u4f18\u5148 *](#-First-things-first!/\u8981\u4e8b\u4f18\u5148-*)\n",
        "        - [> Strings can be tricky sometimes/\u5fae\u5999\u7684\u5b57\u7b26\u4e32 *](#-strings-can-be-tricky-sometimes\u5fae\u5999\u7684\u5b57\u7b26\u4e32-)\n",
        "        - [> Be careful with chained operations/\u5c0f\u5fc3\u94fe\u5f0f\u64cd\u4f5c](#-be-careful-with-chained-operations\u5c0f\u5fc3\u94fe\u5f0f\u64cd\u4f5c)\n",
        "        - [> How not to use `is` operator/\u4e3a\u4ec0\u4e48\u4e0d\u4f7f\u7528 `is` \u64cd\u4f5c\u7b26](#-How-not-to-use-is-operator/\u4e3a\u4ec0\u4e48\u4e0d\u4f7f\u7528-is-\u64cd\u4f5c\u7b26-)\n",
        "        - [> Hash brownies/\u662f\u65f6\u5019\u6765\u70b9\u86cb\u7cd5\u4e86!](#-Hash-brownies\u662f\u65f6\u5019\u6765\u70b9\u86cb\u7cd5\u4e86)\n",
        "        - [> Deep down, we're all the same./\u672c\u8d28\u4e0a,\u6211\u4eec\u90fd\u4e00\u6837. *](#-deep-down-were-all-the-same\u672c\u8d28\u4e0a\u6211\u4eec\u90fd\u4e00\u6837-)\n",
        "        - [> Disorder within order/\u6709\u5e8f\u4e2d\u6f5c\u85cf\u7740\u65e0\u5e8f *](#-disorder-within-order/\u6709\u5e8f\u4e2d\u6f5c\u85cf\u7740\u65e0\u5e8f-*)\n",
        "        - [> Keep trying.../\u4e0d\u505c\u7684try *](#-Keep-trying\u4e0d\u505c\u7684try-)\n",
        "        - [> For what?/\u4e3a\u4ec0\u4e48?](#-for-what\u4e3a\u4ec0\u4e48)\n",
        "        - [> Evaluation time discrepancy/\u6267\u884c\u65f6\u673a\u5dee\u5f02](#-evaluation-time-discrepancy\u6267\u884c\u65f6\u673a\u5dee\u5f02)\n",
        "        - [> `is not ...` is not `is (not ...)` / `is not ...` \u4e0d\u662f `is (not ...)`](#-is-not--is-not-is-not-is-not--\u4e0d\u662f-is-not-)\n",
        "        - [> A tic-tac-toe where X wins in the first attempt!/\u4e00\u8e74\u5373\u81f3!](#-a-tic-tac-toe-where-x-wins-in-the-first-attempt\u4e00\u8e74\u5373\u81f3)\n",
        "        - [> Schr\u00f6dinger's variable/\u859b\u5b9a\u8c14\u7684\u53d8\u91cf *](#-Schr\u00f6dingers-variable\u859b\u5b9a\u8c14\u7684\u53d8\u91cf-)\n",
        "        - [> The chicken-egg problem/\u5148\u6709\u9e21\u8fd8\u662f\u5148\u6709\u86cb *](#-the-chicken-egg-problem/\u5148\u6709\u9e21\u8fd8\u662f\u5148\u6709\u86cb-*)\n",
        "        - [> Subclass relationships/\u5b50\u7c7b\u5173\u7cfb *](#-subclass-relationships\u5b50\u7c7b\u5173\u7cfb-)\n",
        "        - [> Methods equality and identity/\u65b9\u6cd5\u7684\u76f8\u7b49\u6027\u548c\u552f\u4e00\u6027 *](#-Methods-equality-and-identity/\u65b9\u6cd5\u7684\u76f8\u7b49\u6027\u548c\u552f\u4e00\u6027-)\n",
        "        - [> All-true-ation/\u8fd4\u56deTrue\u7684all\u51fd\u6570 *](#-All-true-ation/\u8fd4\u56deTrue\u7684all\u51fd\u6570-)\n",
        "        - [> The surprising comma/\u610f\u5916\u7684\u9017\u53f7](#-the-surprising-comma\u610f\u5916\u7684\u9017\u53f7)\n",
        "        - [> Strings and the backslashes/\u5b57\u7b26\u4e32\u4e0e\u53cd\u659c\u6760](#-strings-and-the-backslashes\u5b57\u7b26\u4e32\u4e0e\u53cd\u659c\u6760)\n",
        "        - [> not knot!/\u522b\u7ea0\u7ed3!](#-not-knot\u522b\u7ea0\u7ed3)\n",
        "        - [> Half triple-quoted strings/\u4e09\u4e2a\u5f15\u53f7](#-half-triple-quoted-strings\u4e09\u4e2a\u5f15\u53f7)\n",
        "        - [> What's wrong with booleans?/\u5e03\u5c14\u4f60\u548b\u4e86?](#-whats-wrong-with-booleans\u5e03\u5c14\u4f60\u548b\u4e86)\n",
        "        - [> Class attributes and instance attributes/\u7c7b\u5c5e\u6027\u548c\u5b9e\u4f8b\u5c5e\u6027](#-class-attributes-and-instance-attributes\u7c7b\u5c5e\u6027\u548c\u5b9e\u4f8b\u5c5e\u6027)\n",
        "        - [> yielding None/\u751f\u6210 None](#-yielding-none\u751f\u6210-none)\n",
        "        - [> Yielding from... return!/\u751f\u6210\u5668\u91cc\u7684return *](#-Yielding-from-return/\u751f\u6210\u5668\u91cc\u7684return-)\n",
        "        - [> Nan-reflexivity/Nan\u7684\u81ea\u53cd\u6027](#-Nan-reflexivityNan\u7684\u81ea\u53cd\u6027)\n",
        "        - [> Mutating the immutable!/\u5f3a\u4eba\u6240\u96be](#-mutating-the-immutable\u5f3a\u4eba\u6240\u96be)\n",
        "        - [> The disappearing variable from outer scope/\u6d88\u5931\u7684\u5916\u90e8\u53d8\u91cf](#-the-disappearing-variable-from-outer-scope\u6d88\u5931\u7684\u5916\u90e8\u53d8\u91cf)\n",
        "        - [> The mysterious key type conversion/\u795e\u79d8\u7684\u952e\u578b\u8f6c\u6362 *](#-the-mysterious-key-type-conversion\u795e\u79d8\u7684\u952e\u578b\u8f6c\u6362-)\n",
        "        - [> Let's see if you can guess this?/\u770b\u770b\u4f60\u80fd\u5426\u731c\u5230\u8fd9\u4e00\u70b9?](#-lets-see-if-you-can-guess-this\u770b\u770b\u4f60\u80fd\u5426\u731c\u5230\u8fd9\u4e00\u70b9)\n",
        "        - [> Exceeds the limit for integer string conversion/\u6574\u578b\u8f6c\u5b57\u7b26\u4e32\u8d8a\u754c](#-exceeds-the-limit-for-integer-string-conversion\u6574\u578b\u8f6c\u5b57\u7b26\u4e32\u8d8a\u754c)\n",
        "    - [Section: Slippery Slopes/\u6ed1\u5761\u8c2c\u8bef](#section-slippery-slopes\u6ed1\u5761\u8c2c\u8bef)\n",
        "        - [> Modifying a dictionary while iterating over it/\u8fed\u4ee3\u5b57\u5178\u65f6\u7684\u4fee\u6539](#-modifying-a-dictionary-while-iterating-over-it\u8fed\u4ee3\u5b57\u5178\u65f6\u7684\u4fee\u6539)\n",
        "        - [> Stubborn `del` operator/\u575a\u5f3a\u7684 `del` *](#-stubborn-del-operator\u575a\u5f3a\u7684-del-)\n",
        "        - [> The out of scope variable/\u5916\u90e8\u4f5c\u7528\u57df\u53d8\u91cf](#-the-out-of-scope-variable\u5916\u90e8\u4f5c\u7528\u57df\u53d8\u91cf)\n",
        "        - [> Deleting a list item while iterating/\u8fed\u4ee3\u5217\u8868\u65f6\u5220\u9664\u5143\u7d20](#-deleting-a-list-item-while-iterating\u8fed\u4ee3\u5217\u8868\u65f6\u5220\u9664\u5143\u7d20)\n",
        "        - [> Lossy zip of iterators/\u4e22\u4e09\u843d\u56db\u7684zip *](#->-Lossy-zip-of-iterators/\u4e22\u4e09\u843d\u56db\u7684zip-)\n",
        "        - [> Loop variables leaking out!/\u5faa\u73af\u53d8\u91cf\u6cc4\u6f0f!](#-loop-variables-leaking-out\u5faa\u73af\u53d8\u91cf\u6cc4\u6f0f)\n",
        "        - [> Beware of default mutable arguments!/\u5f53\u5fc3\u9ed8\u8ba4\u7684\u53ef\u53d8\u53c2\u6570!](#-beware-of-default-mutable-arguments\u5f53\u5fc3\u9ed8\u8ba4\u7684\u53ef\u53d8\u53c2\u6570)\n",
        "        - [> Catching the Exceptions/\u6355\u83b7\u5f02\u5e38](#-catching-the-exceptions\u6355\u83b7\u5f02\u5e38)\n",
        "        - [> Same operands, different story!/\u540c\u4eba\u4e0d\u540c\u547d!](#-same-operands-different-story\u540c\u4eba\u4e0d\u540c\u547d)\n",
        "        - [> Name resolution ignoring class scope/\u5ffd\u7565\u7c7b\u4f5c\u7528\u57df\u7684\u540d\u79f0\u89e3\u6790](#-name-resolution-ignoring-class-scope\u5ffd\u7565\u7c7b\u4f5c\u7528\u57df\u7684\u540d\u79f0\u89e3\u6790)\n",
        "        - [> Rounding like a banker/\u50cf\u94f6\u884c\u5bb6\u4e00\u6837\u820d\u5165 *](#-rounding-like-a-banker/\u50cf\u94f6\u884c\u5bb6\u4e00\u6837\u820d\u5165-)\n",
        "        - [> Needles in a Haystack/\u5927\u6d77\u635e\u9488](#-needles-in-a-haystack\u5927\u6d77\u635e\u9488)\n",
        "        - [> Splitsies/\u5206\u5272\u51fd\u6570](#-Splitsies\u5206\u5272\u51fd\u6570-)\n",
        "        - [> Wild imports/\u901a\u914d\u7b26\u5bfc\u5165\u65b9\u5f0f *](#-Wild-imports\u901a\u914d\u7b26\u5bfc\u5165\u65b9\u5f0f-)\n",
        "        - [> All sorted?/\u90fd\u6392\u5e8f\u4e86\u5417\uff1f *](#-All-sorted\u90fd\u6392\u5e8f\u4e86\u5417-)\n",
        "        - [> Midnight time doesn't exist?/\u4e0d\u5b58\u5728\u7684\u5348\u591c?](#-midnight-time-doesnt-exist\u4e0d\u5b58\u5728\u7684\u5348\u591c)\n",
        "    - [Section: The Hidden treasures!/\u9690\u85cf\u7684\u5b9d\u85cf!](#section-the-hidden-treasures\u9690\u85cf\u7684\u5b9d\u85cf)\n",
        "        - [> Okay Python, Can you make me fly?/Python, \u53ef\u5426\u5e26\u6211\u98de? *](#-okay-python-can-you-make-me-flypython-\u53ef\u5426\u5e26\u6211\u98de-)\n",
        "        - [> `goto`, but why?/`goto`, \u4f46\u4e3a\u4ec0\u4e48? *](#-goto-but-whygoto-\u4f46\u4e3a\u4ec0\u4e48-)\n",
        "        - [> Brace yourself!/\u505a\u597d\u601d\u60f3\u51c6\u5907 *](#-brace-yourself\u505a\u597d\u601d\u60f3\u51c6\u5907-)\n",
        "        - [> Let's meet Friendly Language Uncle For Life/\u8ba9\u751f\u6d3b\u66f4\u53cb\u597d *](#-lets-meet-friendly-language-uncle-for-life\u8ba9\u751f\u6d3b\u66f4\u53cb\u597d-)\n",
        "        - [> Even Python understands that love is complicated/\u8fdePython\u4e5f\u77e5\u9053\u7231\u662f\u96be\u8a00\u7684 *](#-even-python-understands-that-love-is-complicated\u8fdePython\u4e5f\u77e5\u9053\u7231\u662f\u96be\u8a00\u7684-)\n",
        "        - [> Yes, it exists!/\u662f\u7684, \u5b83\u5b58\u5728!](#-yes-it-exists\u662f\u7684-\u5b83\u5b58\u5728)\n",
        "        - [> Ellipsis/\u7701\u7565 *](#-Ellipsis\u7701\u7565-)\n",
        "        - [> Inpinity/\u65e0\u9650 *](#-inpinity\u65e0\u9650-)\n",
        "        - [> Let's mangle/\u4fee\u9970\u65f6\u95f4! *](#-Lets-mangle\u4fee\u9970\u65f6\u95f4-)\n",
        "    - [Section: Appearances are deceptive!/\u5916\u8868\u662f\u9760\u4e0d\u4f4f\u7684!](#section-appearances-are-deceptive\u5916\u8868\u662f\u9760\u4e0d\u4f4f\u7684)\n",
        "        - [> Skipping lines?/\u8df3\u8fc7\u4e00\u884c?](#-skipping-lines\u8df3\u8fc7\u4e00\u884c)\n",
        "        - [> Teleportation/\u7a7a\u95f4\u79fb\u52a8 *](#-teleportation\u7a7a\u95f4\u79fb\u52a8-)\n",
        "        - [> Well, something is fishy.../\u55ef, \u6709\u4e9b\u53ef\u7591...](#-well-something-is-fishy\u55ef\u6709\u4e9b\u53ef\u7591)\n",
        "    - [Section: Miscellaneous/\u6742\u9879](#section-miscellaneous\u6742\u9879)\n",
        "        - [> `+=` is faster/\u66f4\u5feb\u7684 `+=` ](#--is-faster\u66f4\u5feb\u7684-)\n",
        "        - [> Let's make a giant string!/\u6765\u505a\u4e2a\u5de8\u5927\u7684\u5b57\u7b26\u4e32\u5427!](#-lets-make-a-giant-string\u6765\u505a\u4e2a\u5de8\u5927\u7684\u5b57\u7b26\u4e32\u5427)\n",
        "        - [> Slowing down `dict` lookups/\u8ba9\u5b57\u5178\u7684\u67e5\u627e\u6162\u4e0b\u6765 *](#-Slowing-down-dict-lookups\u8ba9\u5b57\u5178\u7684\u67e5\u627e\u6162\u4e0b\u6765-)\n",
        "        - [> Bloating instance `dict`s/\u53d8\u81c3\u80bf\u7684`dict`\u5b9e\u4f8b\u4eec *](#-Bloating-instance-dicts/\u53d8\u81c3\u80bf\u7684dict\u5b9e\u4f8b\u4eec-)\n",
        "        - [> Minor Ones/\u5c0f\u77e5\u8bc6\u70b9](#-minor-ones\u5c0f\u77e5\u8bc6\u70b9)\n",
        "- [Contributing/\u8d21\u732e](#contributing\u8d21\u732e)\n",
        "- [Acknowledgements/\u81f4\u8c22](#acknowledgements\u81f4\u8c22)\n",
        "- [\ud83c\udf93 License/\u8bb8\u53ef](#-license\u8bb8\u53ef)\n",
        "    - [Help/\u5e2e\u52a9](#help\u5e2e\u52a9)\n",
        "    - [Surprise your geeky pythonist friends?/\u60f3\u7ed9\u4f60\u7684\u6781\u5ba2\u670b\u53cb\u4e00\u4e2a\u60ca\u559c?](#surprise-your-geeky-pythonist-friends\u60f3\u7ed9\u4f60\u7684\u6781\u5ba2\u670b\u53cb\u4e00\u4e2a\u60ca\u559c)\n",
        "    - [Need a pdf version?/\u9700\u8981\u6765\u4e00\u4efdpdf\u7248\u7684?](#need-a-pdf-version\u9700\u8981\u6765\u4e00\u4efdpdf\u7248\u7684)\n",
        "    - [Follow Commit/\u8ffd\u8e2aCommit](#follow-commit\u8ffd\u8e2aCommit)\n",
        "    - [996.icu](#996icu)\n",
        "\n",
        "<!-- /TOC -->\n",
        "\n",
        "# Structure of the Examples/\u793a\u4f8b\u7ed3\u6784\n",
        "\n",
        "\u6240\u6709\u793a\u4f8b\u7684\u7ed3\u6784\u90fd\u5982\u4e0b\u6240\u793a:\n",
        "\n",
        "> ### > \u4e00\u4e2a\u7cbe\u9009\u7684\u6807\u9898 *\n",
        "> \u6807\u9898\u672b\u5c3e\u7684\u661f\u53f7\u8868\u793a\u8be5\u793a\u4f8b\u5728\u7b2c\u4e00\u7248\u4e2d\u4e0d\u5b58\u5728\uff0c\u662f\u6700\u8fd1\u6dfb\u52a0\u7684.\n",
        ">\n",
        "> ```py\n",
        "> # \u51c6\u5907\u4ee3\u7801.\n",
        "> # \u91ca\u653e\u9b54\u6cd5...\n",
        "> ```\n",
        ">\n",
        "> **Output (Python version):**\n",
        "> ```py\n",
        "> >>> \u89e6\u53d1\u8bed\u53e5\n",
        "> \u51fa\u4e4e\u610f\u6599\u7684\u8f93\u51fa\u7ed3\u679c\n",
        "> ```\n",
        "> (\u53ef\u9009): \u5bf9\u610f\u5916\u8f93\u51fa\u7ed3\u679c\u7684\u7b80\u77ed\u63cf\u8ff0.\n",
        ">\n",
        ">\n",
        "> #### \ud83d\udca1 \u8bf4\u660e:\n",
        ">\n",
        "> * \u7b80\u8981\u8bf4\u660e\u53d1\u751f\u4e86\u4ec0\u4e48\u4ee5\u53ca\u4e3a\u4ec0\u4e48\u4f1a\u53d1\u751f.\n",
        ">   ```py\n",
        ">   \u5982\u6709\u5fc5\u8981, \u4e3e\u4f8b\u8bf4\u660e\n",
        ">   ```\n",
        ">   **Output:**\n",
        ">   ```py\n",
        ">   >>> \u89e6\u53d1\u8bed\u53e5 # \u4e00\u4e9b\u8ba9\u9b54\u6cd5\u53d8\u5f97\u5bb9\u6613\u7406\u89e3\u7684\u4f8b\u5b50\n",
        ">   # \u4e00\u4e9b\u6b63\u5e38\u7684\u8f93\u5165\n",
        ">   ```\n",
        "\n",
        "**\u6ce8\u610f:** \u6240\u6709\u7684\u793a\u4f8b\u90fd\u5728 Python 3.5.2 \u7248\u672c\u7684\u4ea4\u4e92\u89e3\u91ca\u5668\u4e0a\u6d4b\u8bd5\u8fc7, \u5982\u679c\u4e0d\u7279\u522b\u8bf4\u660e\u5e94\u8be5\u9002\u7528\u4e8e\u6240\u6709 Python \u7248\u672c.\n",
        "\n",
        "# Usage/\u7528\u6cd5\n",
        "\n",
        "\u6211\u4e2a\u4eba\u5efa\u8bae, \u6700\u597d\u4f9d\u6b21\u9605\u8bfb\u4e0b\u9762\u7684\u793a\u4f8b, \u5e76\u5bf9\u6bcf\u4e2a\u793a\u4f8b:\n",
        "- \u4ed4\u7ec6\u9605\u8bfb\u8bbe\u7f6e\u4f8b\u5b50\u6700\u5f00\u59cb\u7684\u4ee3\u7801.  \u5982\u679c\u60a8\u662f\u4e00\u4f4d\u7ecf\u9a8c\u4e30\u5bcc\u7684 Python \u7a0b\u5e8f\u5458, \u90a3\u4e48\u5927\u591a\u6570\u65f6\u5019\u60a8\u90fd\u80fd\u6210\u529f\u9884\u671f\u5230\u540e\u9762\u7684\u7ed3\u679c.\n",
        "- \u9605\u8bfb\u8f93\u51fa\u7ed3\u679c,\n",
        "  + \u786e\u8ba4\u7ed3\u679c\u662f\u5426\u5982\u4f60\u6240\u6599.\n",
        "  + \u786e\u8ba4\u4f60\u662f\u5426\u77e5\u9053\u8fd9\u80cc\u540e\u7684\u539f\u7406.\n",
        "    - \u5982\u679c\u4e0d\u77e5\u9053, \u6df1\u547c\u5438\u7136\u540e\u9605\u8bfb\u8bf4\u660e (\u5982\u679c\u4f60\u8fd8\u662f\u770b\u4e0d\u660e\u767d, \u522b\u6c89\u9ed8! \u53ef\u4ee5\u5728[\u8fd9](https://github.com/satwikkansal/wtfPython)\u63d0\u4e2a issue).\n",
        "    - \u5982\u679c\u77e5\u9053, \u7ed9\u81ea\u5df1\u70b9\u5956\u52b1, \u7136\u540e\u53bb\u770b\u4e0b\u4e00\u4e2a\u4f8b\u5b50.\n",
        "\n",
        "PS: \u4f60\u4e5f\u53ef\u4ee5\u5728\u547d\u4ee4\u884c\u9605\u8bfb WTFpython. \u6211\u4eec\u6709 pypi \u5305 \u548c npm \u5305(\u652f\u6301\u4ee3\u7801\u9ad8\u4eae).(\u8bd1: \u8fd9\u4e24\u4e2a\u90fd\u662f\u82f1\u6587\u7248\u7684)\n",
        "\n",
        "\u5b89\u88c5 npm \u5305 [`wtfpython`](https://www.npmjs.com/package/wtfpython)\n",
        "```sh\n",
        "$ npm install -g wtfpython\n",
        "```\n",
        "\n",
        "\u6216\u8005, \u5b89\u88c5 pypi \u5305 [`wtfpython`](https://pypi.python.org/pypi/wtfpython)\n",
        "```sh\n",
        "$ pip install wtfpython -U\n",
        "```\n",
        "\n",
        "\u73b0\u5728, \u5728\u547d\u4ee4\u884c\u4e2d\u8fd0\u884c `wtfpython`, \u4f60\u5c31\u53ef\u4ee5\u5f00\u59cb\u6d4f\u89c8\u4e86.\n",
        "\n",
        "---\n",
        "\n",
        "# \ud83d\udc40 Examples/\u793a\u4f8b\n",
        "\n",
        "\n",
        "\n\n## \u6258\u7ba1\u7b14\u8bb0\u672c\u6307\u5357\n\n\u8fd9\u53ea\u662f\u901a\u8fc7 jupyter notebook \u6d4f\u89c8 wtfpython \u7684\u5b9e\u9a8c\u6027\u5c1d\u8bd5\u3002\u56e0\u4e3a\u4e00\u4e9b\u793a\u4f8b\u662f\u53ea\u8bfb\u7684\uff1a\n- \u5b83\u4eec\u8981\u4e48\u9700\u8981\u6258\u7ba1\u8fd0\u884c\u65f6\u4e0d\u652f\u6301\u7684 Python \u7248\u672c\u3002\n- \u8981\u4e48\u5b83\u4eec\u65e0\u6cd5\u5728\u6b64\u73af\u5883\u4e2d\u590d\u73b0\u3002\n\n\u9884\u671f\u7684\u8f93\u51fa\u5df2\u7ecf\u5b58\u5728\u4e8e\u4ee3\u7801\u5355\u5143\u4e4b\u540e\u7684\u6298\u53e0\u5355\u5143\u4e2d\u3002 Google colab \u63d0\u4f9b Python2\uff082.7\uff09\u548c Python3\uff083.6\uff0c\u9ed8\u8ba4\uff09\u8fd0\u884c\u73af\u5883\u3002 \u60a8\u53ef\u4ee5\u5728\u8fd9\u4e9b Python2 \u7279\u5b9a\u793a\u4f8b\u4e4b\u95f4\u5207\u6362\u3002 \u5bf9\u4e8e\u7279\u5b9a\u4e8e\u5176\u4ed6\u6b21\u8981\u7248\u672c\u7684\u793a\u4f8b\uff0c\u60a8\u53ef\u4ee5\u7b80\u5355\u5730\u53c2\u8003\u6298\u53e0\u7684\u8f93\u51fa\uff08\u76ee\u524d\u65e0\u6cd5\u5728\u6258\u7ba1\u7b14\u8bb0\u672c\u4e2d\u63a7\u5236\u6b21\u8981\u7248\u672c\uff09\u3002 \u60a8\u53ef\u4ee5\u68c0\u67e5\u5f53\u524d\u7684\u6d3b\u52a8\u7248\u672c\n```py\n>>> import sys\n>>> sys.version\n# Prints out Python version here.\n```\n\n\u8bdd\u867d\u5982\u6b64\uff0c\u5927\u591a\u6570\u793a\u4f8b\u90fd\u6309\u9884\u671f\u5de5\u4f5c\u3002 \u5982\u679c\u60a8\u9047\u5230\u4efb\u4f55\u95ee\u9898\uff0c\u8bf7\u968f\u65f6\u67e5\u9605 wtfpython \u4e0a\u7684\u539f\u59cb\u5185\u5bb9\u5e76\u5728 repo \u4e2d\u521b\u5efa\u95ee\u9898\u3002 \u795d\u541b\u987a\u5229\uff01\n---\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Strings can be tricky sometimes/\u5fae\u5999\u7684\u5b57\u7b26\u4e32 *\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140420665652016\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = \"some_string\"\n",
        "id(a)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140420665652016\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(\"some\" + \"_\" + \"string\") # \u6ce8\u610f\u4e24\u4e2a\u7684id\u503c\u662f\u76f8\u540c\u7684.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = \"wtf\"\n",
        "b = \"wtf\"\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = \"wtf!\"\n",
        "b = \"wtf!\"\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True # 3.7 \u7248\u672c\u8fd4\u56de\u7ed3\u679c\u4e3a False.\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a, b = \"wtf!\", \"wtf!\"\n",
        "a is b \n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'a' * 20 is 'aaaaaaaaaaaaaaaaaaaa'\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False # 3.7 \u7248\u672c\u8fd4\u56de\u7ed3\u679c\u4e3a True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'a' * 21 is 'aaaaaaaaaaaaaaaaaaaaa'\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5f88\u597d\u7406\u89e3, \u5bf9\u5427?\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u8fd9\u4e9b\u884c\u4e3a\u662f\u7531\u4e8e Cpython \u5728\u7f16\u8bd1\u4f18\u5316\u65f6, \u67d0\u4e9b\u60c5\u51b5\u4e0b\u4f1a\u5c1d\u8bd5\u4f7f\u7528\u5df2\u7ecf\u5b58\u5728\u7684\u4e0d\u53ef\u53d8\u5bf9\u8c61\u800c\u4e0d\u662f\u6bcf\u6b21\u90fd\u521b\u5efa\u4e00\u4e2a\u65b0\u5bf9\u8c61. (\u8fd9\u79cd\u884c\u4e3a\u88ab\u79f0\u4f5c\u5b57\u7b26\u4e32\u7684\u9a7b\u7559[string interning])\n",
        "- \u53d1\u751f\u9a7b\u7559\u4e4b\u540e, \u8bb8\u591a\u53d8\u91cf\u53ef\u80fd\u6307\u5411\u5185\u5b58\u4e2d\u7684\u76f8\u540c\u5b57\u7b26\u4e32\u5bf9\u8c61. (\u4ece\u800c\u8282\u7701\u5185\u5b58)\n",
        "- \u5728\u4e0a\u9762\u7684\u4ee3\u7801\u4e2d, \u5b57\u7b26\u4e32\u662f\u9690\u5f0f\u9a7b\u7559\u7684. \u4f55\u65f6\u53d1\u751f\u9690\u5f0f\u9a7b\u7559\u5219\u53d6\u51b3\u4e8e\u5177\u4f53\u7684\u5b9e\u73b0. \u8fd9\u91cc\u6709\u4e00\u4e9b\u65b9\u6cd5\u53ef\u4ee5\u7528\u6765\u731c\u6d4b\u5b57\u7b26\u4e32\u662f\u5426\u4f1a\u88ab\u9a7b\u7559:\n",
        "  - \u6240\u6709\u957f\u5ea6\u4e3a 0 \u548c\u957f\u5ea6\u4e3a 1 \u7684\u5b57\u7b26\u4e32\u90fd\u88ab\u9a7b\u7559.\n",
        "  - \u5b57\u7b26\u4e32\u5728\u7f16\u8bd1\u65f6\u88ab\u5b9e\u73b0 (`'wtf'` \u5c06\u88ab\u9a7b\u7559, \u4f46\u662f `''.join(['w', 't', 'f'])` \u5c06\u4e0d\u4f1a\u88ab\u9a7b\u7559)\n",
        "  - \u5b57\u7b26\u4e32\u4e2d\u53ea\u5305\u542b\u5b57\u6bcd\uff0c\u6570\u5b57\u6216\u4e0b\u5212\u7ebf\u65f6\u5c06\u4f1a\u9a7b\u7559. \u6240\u4ee5 `'wtf!'` \u7531\u4e8e\u5305\u542b `!` \u800c\u672a\u88ab\u9a7b\u7559. \u53ef\u4ee5\u5728[\u8fd9\u91cc](https://github.com/python/cpython/blob/3.6/Objects/codeobject.c#L19)\u627e\u5230 CPython \u5bf9\u6b64\u89c4\u5219\u7684\u5b9e\u73b0.\n",
        "\n",
        "    <img src=\"/images/string-intern/string_intern.png\" alt=\"\">\n",
        "\n",
        "- \u5f53\u5728\u540c\u4e00\u884c\u5c06 `a` \u548c `b` \u7684\u503c\u8bbe\u7f6e\u4e3a `\"wtf!\"` \u7684\u65f6\u5019, Python \u89e3\u91ca\u5668\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u5bf9\u8c61, \u7136\u540e\u540c\u65f6\u5f15\u7528\u7b2c\u4e8c\u4e2a\u53d8\u91cf(\u8bd1: \u4ec5\u9002\u7528\u4e8e3.7\u4ee5\u4e0b, \u8be6\u7ec6\u60c5\u51b5\u8bf7\u770b[\u8fd9\u91cc](https://github.com/leisurelicht/wtfpython-cn/issues/13)). \u5982\u679c\u4f60\u5728\u4e0d\u540c\u7684\u884c\u4e0a\u8fdb\u884c\u8d4b\u503c\u64cd\u4f5c, \u5b83\u5c31\u4e0d\u4f1a\u201c\u77e5\u9053\u201d\u5df2\u7ecf\u6709\u4e00\u4e2a `wtf\uff01` \u5bf9\u8c61 (\u56e0\u4e3a `\"wtf!\"` \u4e0d\u662f\u6309\u7167\u4e0a\u9762\u63d0\u5230\u7684\u65b9\u5f0f\u88ab\u9690\u5f0f\u9a7b\u7559\u7684). \u5b83\u662f\u4e00\u79cd\u7f16\u8bd1\u5668\u4f18\u5316, \u7279\u522b\u9002\u7528\u4e8e\u4ea4\u4e92\u5f0f\u73af\u5883.\n",
        "- \u5e38\u91cf\u6298\u53e0(constant folding) \u662f Python \u4e2d\u7684\u4e00\u79cd [\u7aa5\u5b54\u4f18\u5316(peephole optimization)](https://en.wikipedia.org/wiki/Peephole_optimization) \u6280\u672f. \u8fd9\u610f\u5473\u7740\u5728\u7f16\u8bd1\u65f6\u8868\u8fbe\u5f0f `'a'*20` \u4f1a\u88ab\u66ff\u6362\u4e3a `'aaaaaaaaaaaaaaaaaaaa'` \u4ee5\u51cf\u5c11\u8fd0\u884c\u65f6\u7684\u65f6\u949f\u5468\u671f. \u53ea\u6709\u957f\u5ea6\u5c0f\u4e8e 20 \u7684\u5b57\u7b26\u4e32\u624d\u4f1a\u53d1\u751f\u5e38\u91cf\u6298\u53e0. (\u4e3a\u5565? \u60f3\u8c61\u4e00\u4e0b\u7531\u4e8e\u8868\u8fbe\u5f0f `'a'*10**10` \u800c\u751f\u6210\u7684 `.pyc` \u6587\u4ef6\u7684\u5927\u5c0f). \u76f8\u5173\u7684\u6e90\u7801\u5b9e\u73b0\u5728[\u8fd9\u91cc](https://github.com/python/cpython/blob/3.6/Python/peephole.c#L288).\n",
        "- \u5982\u679c\u4f60\u662f\u4f7f\u7528 3.7 \u7248\u672c\u4e2d\u8fd0\u884c\u4e0a\u8ff0\u793a\u4f8b\u4ee3\u7801, \u4f1a\u53d1\u73b0\u90e8\u5206\u4ee3\u7801\u7684\u8fd0\u884c\u7ed3\u679c\u4e0e\u6ce8\u91ca\u8bf4\u660e\u76f8\u540c. \u8fd9\u662f\u56e0\u4e3a\u5728 3.7 \u7248\u672c\u4e2d, \u5e38\u91cf\u6298\u53e0\u5df2\u7ecf\u4ece\u7aa5\u5b54\u4f18\u5316\u5668\u8fc1\u79fb\u81f3\u65b0\u7684 AST \u4f18\u5316\u5668, \u540e\u8005\u53ef\u4ee5\u4ee5\u66f4\u9ad8\u7684\u4e00\u81f4\u6027\u6765\u6267\u884c\u4f18\u5316. (\u7531 Eugene Toder \u548c INADA Naoki \u5728 [bpo-29469](https://bugs.python.org/issue29469) \u548c [bpo-11549](https://bugs.python.org/issue11549) \u4e2d\u8d21\u732e.) \n",
        "- (\u8bd1: \u4f46\u662f\u5728\u6700\u65b0\u7684 3.8 \u7248\u672c\u4e2d, \u7ed3\u679c\u53c8\u53d8\u56de\u53bb\u4e86. \u867d\u7136 3.8 \u7248\u672c\u548c 3.7 \u7248\u672c\u4e00\u6837, \u90fd\u662f\u4f7f\u7528 AST \u4f18\u5316\u5668. \u76ee\u524d\u4e0d\u786e\u5b9a\u5b98\u65b9\u5bf9 3.8 \u7248\u672c\u7684 AST \u505a\u4e86\u4ec0\u4e48\u8c03\u6574.)\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Be careful with chained operations/\u5c0f\u5fc3\u94fe\u5f0f\u64cd\u4f5c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "(False == False) in [False] # \u53ef\u4ee5\u7406\u89e3\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "False == (False in [False]) # \u53ef\u4ee5\u7406\u89e3\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "False == False in [False] # \u4e3a\u6bdb?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "True is False == False\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "False is False is False\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "1 > 0 < 1\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "(1 > 0) < 1\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "1 > (0 < 1)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "\u6839\u636e https://docs.python.org/3/reference/expressions.html#comparisons\n",
        "\n",
        "> \u5f62\u5f0f\u4e0a, \u5982\u679c a, b, c, ..., y, z \u662f\u8868\u8fbe\u5f0f, \u800c op1, op2, ..., opN \u662f\u6bd4\u8f83\u8fd0\u7b97\u7b26, \u90a3\u4e48\u9664\u4e86\u6bcf\u4e2a\u8868\u8fbe\u5f0f\u6700\u591a\u53ea\u51fa\u73b0\u4e00\u6b21\u4ee5\u5916 a op1 b op2 c ... y opN z \u5c31\u7b49\u4e8e a op1 b and b op2 c and ... y opN z.\n",
        "\n",
        "\u867d\u7136\u4e0a\u9762\u7684\u4f8b\u5b50\u4f3c\u4e4e\u5f88\u611a\u8822, \u4f46\u662f\u50cf `a == b == c` \u6216 `0 <= x <= 100` \u5c31\u5f88\u68d2\u4e86.\n",
        "\n",
        "* `False is False is False` \u76f8\u5f53\u4e8e `(False is False) and (False is False)`\n",
        "* `True is False == False` \u76f8\u5f53\u4e8e `(True is False) and (False == False)`, \u7531\u4e8e\u8bed\u53e5\u7684\u7b2c\u4e00\u90e8\u5206 (`True is False`) \u7b49\u4e8e `False`, \u56e0\u6b64\u6574\u4e2a\u8868\u8fbe\u5f0f\u7684\u7ed3\u679c\u4e3a `False`.\n",
        "* `1 > 0 < 1` \u76f8\u5f53\u4e8e `(1 > 0) and (0 < 1)`, \u6240\u4ee5\u6700\u7ec8\u7ed3\u679c\u4e3a `True`.\n",
        "* \u8868\u8fbe\u5f0f `(1 > 0) < 1` \u76f8\u5f53\u4e8e `True < 1` \u4e14\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  int(True)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  True + 1 # \u4e0e\u8fd9\u4e2a\u4f8b\u5b50\u65e0\u5173\uff0c\u53ea\u662f\u5a31\u4e50\u4e00\u4e0b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  \u6240\u4ee5, `1 < 1` \u7b49\u4e8e `False`\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > How not to use `is` operator/\u4e3a\u4ec0\u4e48\u4e0d\u4f7f\u7528 `is` \u64cd\u4f5c\u7b26\n",
        "\u4e0b\u9762\u662f\u4e00\u4e2a\u5728\u4e92\u8054\u7f51\u4e0a\u975e\u5e38\u6709\u540d\u7684\u4f8b\u5b50.\n",
        "\n",
        "1\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = 256\n",
        "b = 256\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = 257\n",
        "b = 257\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = []\n",
        "b = []\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = tuple()\n",
        "b = tuple()\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n",
        "**Output**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a, b = 257, 257\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 3.7.x specifically)**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a, b = 257, 257\n",
        "a is b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "**`is` \u548c `==` \u7684\u533a\u522b**\n",
        "\n",
        "* `is` \u8fd0\u7b97\u7b26\u68c0\u67e5\u4e24\u4e2a\u8fd0\u7b97\u5bf9\u8c61\u662f\u5426\u5f15\u7528\u81ea\u540c\u4e00\u5bf9\u8c61 (\u5373, \u5b83\u68c0\u67e5\u4e24\u4e2a\u8fd0\u7b97\u5bf9\u8c61\u662f\u5426\u76f8\u540c).\n",
        "* `==` \u8fd0\u7b97\u7b26\u6bd4\u8f83\u4e24\u4e2a\u8fd0\u7b97\u5bf9\u8c61\u7684\u503c\u662f\u5426\u76f8\u7b49.\n",
        "* \u56e0\u6b64 `is` \u4ee3\u8868\u5f15\u7528\u76f8\u540c, `==` \u4ee3\u8868\u503c\u76f8\u7b49. \u4e0b\u9762\u7684\u4f8b\u5b50\u53ef\u4ee5\u5f88\u597d\u7684\u8bf4\u660e\u8fd9\u70b9,\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  [] == []\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  [] is [] # \u8fd9\u4e24\u4e2a\u7a7a\u5217\u8868\u4f4d\u4e8e\u4e0d\u540c\u7684\u5185\u5b58\u5730\u5740.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**`256` \u662f\u4e00\u4e2a\u5df2\u7ecf\u5b58\u5728\u7684\u5bf9\u8c61, \u800c `257` \u4e0d\u662f**\n",
        "\n",
        "\u5f53\u4f60\u542f\u52a8Python \u7684\u65f6\u5019, \u6570\u503c\u4e3a `-5` \u5230 `256` \u7684\u5bf9\u8c61\u5c31\u5df2\u7ecf\u88ab\u5206\u914d\u597d\u4e86. \u8fd9\u4e9b\u6570\u5b57\u56e0\u4e3a\u7ecf\u5e38\u88ab\u4f7f\u7528, \u6240\u4ee5\u4f1a\u88ab\u63d0\u524d\u51c6\u5907\u597d.\n",
        "\n",
        "Python \u901a\u8fc7\u8fd9\u79cd\u521b\u5efa\u5c0f\u6574\u6570\u6c60\u7684\u65b9\u5f0f\u6765\u907f\u514d\u5c0f\u6574\u6570\u9891\u7e41\u7684\u7533\u8bf7\u548c\u9500\u6bc1\u5185\u5b58\u7a7a\u95f4.\n",
        "\n",
        "\u5f15\u7528\u81ea https://docs.python.org/3/c-api/long.html\n",
        "> \u5f53\u524d\u7684\u5b9e\u73b0\u4e3a-5\u5230256\u4e4b\u95f4\u7684\u6240\u6709\u6574\u6570\u4fdd\u7559\u4e00\u4e2a\u6574\u6570\u5bf9\u8c61\u6570\u7ec4, \u5f53\u4f60\u521b\u5efa\u4e86\u4e00\u4e2a\u8be5\u8303\u56f4\u5185\u7684\u6574\u6570\u65f6, \u4f60\u53ea\u9700\u8981\u8fd4\u56de\u73b0\u6709\u5bf9\u8c61\u7684\u5f15\u7528. \u6240\u4ee5\u6539\u53d81\u7684\u503c\u662f\u6709\u53ef\u80fd\u7684. \u6211\u6000\u7591\u8fd9\u79cd\u884c\u4e3a\u5728Python\u4e2d\u662f\u672a\u5b9a\u4e49\u884c\u4e3a. :-)\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "10922528\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(256)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "10922528\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = 256\n",
        "b = 256\n",
        "id(a)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "10922528\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(b)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140084850247312\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(257)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140084850247440\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = 257\n",
        "y = 257\n",
        "id(x)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140084850247344\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(y)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8fd9\u91cc\u89e3\u91ca\u5668\u5e76\u6ca1\u6709\u667a\u80fd\u5230\u80fd\u5728\u6267\u884c `y = 257` \u65f6\u610f\u8bc6\u5230\u6211\u4eec\u5df2\u7ecf\u521b\u5efa\u4e86\u4e00\u4e2a\u6574\u6570 `257`, \u6240\u4ee5\u5b83\u5728\u5185\u5b58\u4e2d\u53c8\u65b0\u5efa\u4e86\u53e6\u4e00\u4e2a\u5bf9\u8c61.\n",
        "\n",
        "\u7c7b\u4f3c\u7684\u4f18\u5316\u4e5f\u9002\u7528\u4e8e\u5176\u4ed6**\u4e0d\u53ef\u53d8**\u5bf9\u8c61\uff0c\u4f8b\u5982\u7a7a\u5143\u7ec4\u3002\u7531\u4e8e\u5217\u8868\u662f\u53ef\u53d8\u7684\uff0c\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48 `[] is []` \u5c06\u8fd4\u56de `False` \u800c `() is ()` \u5c06\u8fd4\u56de `True`\u3002 \u8fd9\u89e3\u91ca\u4e86\u6211\u4eec\u7684\u7b2c\u4e8c\u4e2a\u4ee3\u7801\u6bb5\u3002\u800c\u7b2c\u4e09\u4e2a\u5462\uff1a\n",
        "\n",
        "**\u5f53 `a` \u548c `b` \u5728\u540c\u4e00\u884c\u4e2d\u4f7f\u7528\u76f8\u540c\u7684\u503c\u521d\u59cb\u5316\u65f6\uff0c\u4f1a\u6307\u5411\u540c\u4e00\u4e2a\u5bf9\u8c61.**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140640774013296\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a, b = 257, 257\n",
        "id(a)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140640774013296\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(b)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140640774013392\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = 257\n",
        "b = 257\n",
        "id(a)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "140640774013488\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(b)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5f53 a \u548c b \u5728\u540c\u4e00\u884c\u4e2d\u88ab\u8bbe\u7f6e\u4e3a `257` \u65f6, Python \u89e3\u91ca\u5668\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u5bf9\u8c61, \u7136\u540e\u540c\u65f6\u5f15\u7528\u7b2c\u4e8c\u4e2a\u53d8\u91cf. \u5982\u679c\u4f60\u5728\u4e0d\u540c\u7684\u884c\u4e0a\u8fdb\u884c, \u5b83\u5c31\u4e0d\u4f1a \"\u77e5\u9053\" \u5df2\u7ecf\u5b58\u5728\u4e00\u4e2a `257` \u5bf9\u8c61\u4e86.\n",
        "* \u8fd9\u662f\u4e00\u79cd\u7279\u522b\u4e3a\u4ea4\u4e92\u5f0f\u73af\u5883\u505a\u7684\u7f16\u8bd1\u5668\u4f18\u5316. \u5f53\u4f60\u5728\u5b9e\u65f6\u89e3\u91ca\u5668\u4e2d\u8f93\u5165\u4e24\u884c\u7684\u65f6\u5019, \u4ed6\u4eec\u4f1a\u5355\u72ec\u7f16\u8bd1, \u56e0\u6b64\u4e5f\u4f1a\u5355\u72ec\u8fdb\u884c\u4f18\u5316. \u5982\u679c\u4f60\u5728 `.py` \u6587\u4ef6\u4e2d\u5c1d\u8bd5\u8fd9\u4e2a\u4f8b\u5b50, \u5219\u4e0d\u4f1a\u770b\u5230\u76f8\u540c\u7684\u884c\u4e3a, \u56e0\u4e3a\u6587\u4ef6\u662f\u4e00\u6b21\u6027\u7f16\u8bd1\u7684\u3002\u8fd9\u79cd\u4f18\u5316\u4e0d\u4ec5\u9650\u4e8e\u6574\u6570\uff0c\u5b83\u4e5f\u9002\u7528\u4e8e\u5176\u4ed6\u4e0d\u53ef\u53d8\u6570\u636e\u7c7b\u578b\uff0c\u4f8b\u5982\u5b57\u7b26\u4e32\uff08\u67e5\u770b\u793a\u4f8b\u201c\u5fae\u5999\u7684\u5b57\u7b26\u4e32\u201d\uff09\u548c\u6d6e\u70b9\u6570\uff0c\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  a, b = 257.0, 257.0\n",
        "  a is b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u4e3a\u4ec0\u4e48\u8fd9\u4e0d\u9002\u7528\u4e8e Python 3.7\uff1f \u5927\u6982\u662f\u56e0\u4e3a\u6b64\u7c7b\u7f16\u8bd1\u5668\u4f18\u5316\u662f\u7279\u5b9a\u4e8e\u5b9e\u73b0\u7684\uff08\u5373\u53ef\u80fd\u968f\u7248\u672c\u3001\u64cd\u4f5c\u7cfb\u7edf\u7b49\u800c\u53d8\u5316\uff09\u3002\u6211\u4ecd\u5728\u8bd5\u56fe\u5f04\u6e05\u695a\u5bfc\u81f4\u95ee\u9898\u7684\u5177\u4f53\u5b9e\u73b0\u66f4\u6539\uff0c\u60a8\u53ef\u4ee5\u67e5\u770b\u6b64 [\u95ee\u9898](https://github.com/satwikkansal/wtfpython/issues/100) \u4ee5\u83b7\u53d6\u66f4\u65b0\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Hash brownies/\u662f\u65f6\u5019\u6765\u70b9\u86cb\u7cd5\u4e86!\n",
        "* hash brownie\u6307\u4e00\u79cd\u542b\u6709\u5927\u9ebb\u6210\u5206\u7684\u86cb\u7cd5, \u6240\u4ee5\u8fd9\u91cc\u662f\u53e5\u53cc\u5173\n",
        "* \u8fd9\u91cc\u4fdd\u7559\u539f\u4f5c\u8005\u5bf9\u4e8e\u6807\u9898\u7684\u7ffb\u8bd1\n",
        "<!-- Example ID: eb17db53-49fd-4b61-85d6-345c5ca213ff --->\n",
        "\n",
        "\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict = {}\n",
        "some_dict[5.5] = \"JavaScript\"\n",
        "some_dict[5.0] = \"Ruby\"\n",
        "some_dict[5] = \"Python\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\"JavaScript\"\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict[5.5]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\"Python\"\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict[5.0] # \"Python\" \u6d88\u9664\u4e86 \"Ruby\" \u7684\u5b58\u5728?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\"Python\"\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict[5] \n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "complex\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "complex_five = 5 + 0j\n",
        "type(complex_five)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\"Python\"\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict[complex_five]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4e3a\u4ec0\u4e48\u5230\u5904\u90fd\u662fPython?\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "\n",
        "* \u8fd9\u4e2a StackOverflow\u7684 [\u56de\u7b54](https://stackoverflow.com/a/32211042/4354153) \u6f02\u4eae\u5730\u89e3\u91ca\u4e86\u8fd9\u80cc\u540e\u7684\u57fa\u672c\u539f\u7406.\n",
        "\n",
        "* Python \u5b57\u5178\u4e2d\u952e\u7684\u552f\u4e00\u6027\u662f\u6839\u636e *\u7b49\u4ef7\u6027*\uff0c\u800c\u4e0d\u662f\u540c\u4e00\u6027\u3002 \u56e0\u6b64\uff0c\u5373\u4f7f `5`\u3001`5.0` \u548c `5 + 0j` \u662f\u4e0d\u540c\u7c7b\u578b\u7684\u4e0d\u540c\u5bf9\u8c61\uff0c\u7531\u4e8e\u5b83\u4eec\u662f\u76f8\u7b49\u7684\uff0c\u5b83\u4eec\u4e0d\u80fd\u90fd\u5728\u540c\u4e00\u4e2a `dict`\uff08\u6216 `set`\uff09\u4e2d\u3002 \u53ea\u8981\u60a8\u63d2\u5165\u5176\u4e2d\u4efb\u4f55\u4e00\u4e2a\uff0c\u5c1d\u8bd5\u67e5\u627e\u4efb\u4f55\u4e0d\u540c\u4f46\u7b49\u4ef7\u7684\u952e\u90fd\u5c06\u4f7f\u7528\u539f\u59cb\u6620\u5c04\u503c\u6210\u529f\uff08\u800c\u4e0d\u662f\u56e0\u201cKeyError\u201d\u800c\u5931\u8d25\uff09\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  5 == 5.0 == 5 + 0j\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  5 is not 5.0 is not 5 + 0j\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_dict = {}\n",
        "  some_dict[5.0] = \"Ruby\"\n",
        "  5.0 in some_dict\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  (5 in some_dict) and (5 + 0j in some_dict)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u8fd9\u5728\u8d4b\u503c\u7684\u65f6\u5019\u4e5f\u4f1a\u751f\u6548\u3002\u56e0\u6b64\uff0c\u5f53\u60a8\u6267\u884c `some_dict[5] = \"Python\"` \u65f6\uff0cPython \u4f1a\u627e\u5230\u5177\u6709\u7b49\u4ef7\u952e\u503c `5.0 -> \"Ruby\"` \u7684\u73b0\u6709\u9879\uff0c\u8986\u76d6\u5176\u503c\uff0c\u5e76\u4fdd\u7559\u539f\u59cb\u952e\u503c\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  {5.0: 'Ruby'}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_dict\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  {5.0: 'Python'}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_dict[5] = \"Python\"\n",
        "  some_dict\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "* \u90a3\u4e48\u6211\u4eec\u5982\u4f55\u5c06\u952e\u503c\u66f4\u65b0\u4e3a`5`\uff08\u800c\u4e0d\u662f`5.0`\uff09\uff1f \u6211\u4eec\u5b9e\u9645\u4e0a\u4e0d\u80fd\u539f\u5730\u66f4\u65b0\uff0c\u4f46\u662f\u6211\u4eec\u53ef\u4ee5\u5148\u5220\u9664\u952e\uff08`del some_dict[5.0]`\uff09\uff0c\u7136\u540e\u91cd\u65b0\u8d4b\u503c\uff08`some_dict[5]`\uff09\u5f97\u5230\u6574\u6570`5` \u4f5c\u4e3a\u952e\u800c\u4e0d\u662f\u6d6e\u70b9\u6570 `5.0`\uff0c\u5c3d\u7ba1\u8fd9\u5c5e\u4e8e\u6781\u5c11\u6570\u60c5\u51b5\u3002\n",
        "\n",
        "* Python \u662f\u5982\u4f55\u5728\u5305\u542b `5.0` \u7684\u5b57\u5178\u4e2d\u627e\u5230 `5` \u7684\uff1f Python \u53ea\u9700\u8981\u82b1\u8d39\u5e38\u6570\u65f6\u95f4\uff0c\u800c\u65e0\u9700\u4f7f\u7528\u54c8\u5e0c\u51fd\u6570\u904d\u5386\u6bcf\u4e00\u9879\u3002\u5f53 Python \u5728 dict \u4e2d\u67e5\u627e\u952e `foo` \u65f6\uff0c\u5b83\u9996\u5148\u8ba1\u7b97 `hash(foo)`\uff08\u4ee5\u5e38\u6570\u65f6\u95f4\u8fd0\u884c\uff09\u3002\u56e0\u4e3a\u5728 Python \u4e2d\uff0c\u8981\u6c42\u76f8\u7b49\u7684\u5bf9\u8c61\u5177\u6709\u76f8\u540c\u7684\u54c8\u5e0c\u503c\uff08\u6b64\u5904\u4e3a[\u6587\u6863](https://docs.python.org/3/reference/datamodel.html#object.__hash__)\uff09\uff0c`5` \u3001`5.0` \u548c `5 + 0j` \u5177\u6709\u76f8\u540c\u7684\u54c8\u5e0c\u503c\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  5 == 5.0 == 5 + 0j\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  hash(5) == hash(5.0) == hash(5 + 0j)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **\u6ce8\u610f\uff1a** \u53cd\u4e4b\u4e0d\u4e00\u5b9a\u6b63\u786e\uff1a\u5177\u6709\u76f8\u7b49\u54c8\u5e0c\u503c\u7684\u5bf9\u8c61\u672c\u8eab\u53ef\u80fd\u4e0d\u76f8\u7b49\u3002\uff08\u8fd9\u662f[\u54c8\u5e0c\u51b2\u7a81](https://en.wikipedia.org/wiki/Collision_(computer_science)\uff09\u9020\u6210\u7684\uff0c\u8fd9\u4e5f\u4f1a\u964d\u4f4e\u54c8\u5e0c\u8fd0\u7b97\u7684\u6027\u80fd\u3002\uff09\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Deep down, we're all the same./\u672c\u8d28\u4e0a,\u6211\u4eec\u90fd\u4e00\u6837. *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class WTF:\n",
        "  pass\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "WTF() == WTF() # \u4e24\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61\u5e94\u8be5\u4e0d\u76f8\u7b49\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "WTF() is WTF() # \u4e5f\u4e0d\u76f8\u540c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "hash(WTF()) == hash(WTF()) # \u54c8\u5e0c\u503c\u4e5f\u5e94\u8be5\u4e0d\u540c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "id(WTF()) == id(WTF())\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5f53\u8c03\u7528 `id` \u51fd\u6570\u65f6, Python \u521b\u5efa\u4e86\u4e00\u4e2a `WTF` \u7c7b\u7684\u5bf9\u8c61\u5e76\u4f20\u7ed9 `id` \u51fd\u6570. \u7136\u540e `id` \u51fd\u6570\u83b7\u53d6\u5176id\u503c (\u4e5f\u5c31\u662f\u5185\u5b58\u5730\u5740), \u7136\u540e\u4e22\u5f03\u8be5\u5bf9\u8c61. \u8be5\u5bf9\u8c61\u5c31\u88ab\u9500\u6bc1\u4e86.\n",
        "* \u5f53\u6211\u4eec\u8fde\u7eed\u4e24\u6b21\u8fdb\u884c\u8fd9\u4e2a\u64cd\u4f5c\u65f6, Python\u4f1a\u5c06\u76f8\u540c\u7684\u5185\u5b58\u5730\u5740\u5206\u914d\u7ed9\u7b2c\u4e8c\u4e2a\u5bf9\u8c61. \u56e0\u4e3a (\u5728CPython\u4e2d) `id` \u51fd\u6570\u4f7f\u7528\u5bf9\u8c61\u7684\u5185\u5b58\u5730\u5740\u4f5c\u4e3a\u5bf9\u8c61\u7684id\u503c, \u6240\u4ee5\u4e24\u4e2a\u5bf9\u8c61\u7684id\u503c\u662f\u76f8\u540c\u7684.\n",
        "* \u7efc\u4e0a, \u5bf9\u8c61\u7684id\u503c\u4ec5\u4ec5\u5728\u5bf9\u8c61\u7684\u751f\u547d\u5468\u671f\u5185\u552f\u4e00. \u5728\u5bf9\u8c61\u88ab\u9500\u6bc1\u4e4b\u540e, \u6216\u88ab\u521b\u5efa\u4e4b\u524d, \u5176\u4ed6\u5bf9\u8c61\u53ef\u4ee5\u5177\u6709\u76f8\u540c\u7684id\u503c.\n",
        "* \u90a3\u4e3a\u4ec0\u4e48 `is` \u64cd\u4f5c\u7684\u7ed3\u679c\u4e3a `False` \u5462? \u8ba9\u6211\u4eec\u770b\u770b\u8fd9\u6bb5\u4ee3\u7801.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  class WTF(object):\n",
        "    def __init__(self): print(\"I\")\n",
        "    def __del__(self): print(\"D\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  I\n",
              "  I\n",
              "  D\n",
              "  D\n",
              "  False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  WTF() is WTF()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  I\n",
              "  D\n",
              "  I\n",
              "  D\n",
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  id(WTF()) == id(WTF())\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  \u6b63\u5982\u4f60\u6240\u770b\u5230\u7684, \u5bf9\u8c61\u9500\u6bc1\u7684\u987a\u5e8f\u662f\u9020\u6210\u6240\u6709\u4e0d\u540c\u4e4b\u5904\u7684\u539f\u56e0.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Disorder within order/\u6709\u5e8f\u4e2d\u6f5c\u85cf\u7740\u65e0\u5e8f *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "from collections import OrderedDict\n",
        "\n",
        "dictionary = dict()\n",
        "dictionary[1] = 'a'; dictionary[2] = 'b';\n",
        "\n",
        "ordered_dict = OrderedDict()\n",
        "ordered_dict[1] = 'a'; ordered_dict[2] = 'b';\n",
        "\n",
        "another_ordered_dict = OrderedDict()\n",
        "another_ordered_dict[2] = 'b'; another_ordered_dict[1] = 'a';\n",
        "\n",
        "class DictWithHash(dict):\n",
        "    \"\"\"\n",
        "    \u5b9e\u73b0\u4e86 __hash__ \u9b54\u6cd5\u65b9\u6cd5\u7684dict\u7c7b\n",
        "    \"\"\"\n",
        "    __hash__ = lambda self: 0\n",
        "\n",
        "class OrderedDictWithHash(OrderedDict):\n",
        "    \"\"\"\n",
        "    \u5b9e\u73b0\u4e86 __hash__ \u9b54\u6cd5\u65b9\u6cd5\u7684OrderedDict\u7c7b\n",
        "    \"\"\"\n",
        "    __hash__ = lambda self: 0\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dictionary == ordered_dict # \u5982\u679c a == b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dictionary == another_ordered_dict # \u4e14 b == c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n",
              "\n",
              "# \u4f17\u6240\u5468\u77e5\uff0cset\u6570\u636e\u7ed3\u6784\u50a8\u5b58\u4e0d\u91cd\u590d\u5143\u7d20\uff0c\n",
              "# \u8ba9\u6211\u4eec\u751f\u6210\u4ee5\u4e0a\u5b57\u5178\u7684 set \u6570\u636e\u7c7b\u578b\uff0c\u770b\u770b\u4f1a\u53d1\u751f\u4ec0\u4e48\u2026\u2026\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "ordered_dict == another_ordered_dict # \u90a3\u4e48\u4e3a\u4ec0\u4e48 c == a \u4e0d\u6210\u7acb??\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "TypeError: unhashable type: 'dict'\n",
              "\n",
              "# dict\u7c7b\u6ca1\u6709\u5b9e\u73b0 __hash__ \uff0c\u51fa\u9519\u53ef\u4ee5\u7406\u89e3\uff0c\u63a5\u4e0b\u6765\u4f7f\u7528\u6211\u4eec\u6d3e\u751f\u7684\u7c7b\u3002\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len({dictionary, ordered_dict, another_ordered_dict})\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dictionary = DictWithHash()\n",
        "dictionary[1] = 'a'; dictionary[2] = 'b';\n",
        "ordered_dict = OrderedDictWithHash()\n",
        "ordered_dict[1] = 'a'; ordered_dict[2] = 'b';\n",
        "another_ordered_dict = OrderedDictWithHash()\n",
        "another_ordered_dict[2] = 'b'; another_ordered_dict[1] = 'a';\n",
        "len({dictionary, ordered_dict, another_ordered_dict})\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len({ordered_dict, another_ordered_dict, dictionary}) # \u4ea4\u6362\u987a\u5e8f\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5230\u5e95\u53d1\u751f\u4e86\u4ec0\u4e48?\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u7b49\u53f7\u7684\u4f20\u9012\u6027\u6ca1\u6709\u5728 `dictionary`, `ordered_dict` \u548c `another_ordered_dict` \u4e4b\u95f4\u751f\u6548\u662f `OrderedDict` \u7c7b\u4e2d `__eq__` \u65b9\u6cd5\u7684\u5b9e\u73b0\u65b9\u5f0f\u9020\u6210\u7684\u3002\u6839\u636e[\u6587\u6863](https://docs.python.org/3/library/collections.html#ordereddict-objects)\u4ee5\u4e0b\u90e8\u5206:\n",
        "  \n",
        "    > \u5bf9\u4e8e `OrderedDict` \u7c7b\u4e4b\u95f4\uff0c\u76f8\u7b49\u6027\u7684\u5224\u5b9a\u662f\u4f4d\u7f6e\u654f\u611f\u7684\uff0c\u5b9e\u73b0\u7c7b\u4f3c\u4e8e `list(od1.items())==list(od2.items())`\u3002\u5bf9\u4e8e `OrderedDict` \u7c7b\u4e0e\u5176\u4ed6 `Mapping` \u5bf9\u8c61\uff08\u4f8b\u5982`dict` \u7c7b\uff09\uff0c\u76f8\u7b49\u6027\u7684\u5224\u5b9a\u662f\u975e\u4f4d\u7f6e\u654f\u611f\u7684\u3002\n",
        "- \u8fd9\u662f\u4e3a\u4e86\u4efb\u4f55\u4f7f\u7528\u5e38\u89c4 `dict` \u7c7b\u7684\u5730\u65b9\u80fd\u591f\u76f4\u63a5\u4f7f\u7528 `OrderedDict` \u5bf9\u8c61\u4ee3\u66ff\u3002\n",
        "- \u597d\u5566\uff0c\u90a3\u4e3a\u4ec0\u4e48\u6539\u53d8\u987a\u5e8f\u4f1a\u5f71\u54cd `set` \u5bf9\u8c61\u751f\u6210\u7684\u957f\u5ea6\u5462? \u7b54\u6848\u5c31\u662f\u4e0a\u9762\u8bf4\u7684\u7f3a\u4e4f\u7b49\u53f7\u7684\u4f20\u9012\u6027\u3002\u56e0\u4e3a `set` \u7c7b\u662f\u552f\u4e00\u5143\u7d20\u7684\u65e0\u5e8f\u96c6\u5408\uff0c\u5143\u7d20\u63d2\u5165\u7684\u987a\u5e8f\u4e0d\u5e94\u8be5\u6709\u5f71\u54cd\u3002\u4f46\u5728\u6b64\u4f8b\u4e2d\uff0c\u786e\u6709\u4e0d\u540c\u3002\u8ba9\u6211\u4eec\u8fdb\u4e00\u6b65\u6df1\u5165\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_set = set()\n",
        "    some_set.add(dictionary) # \u6d89\u53ca\u7684\u53d8\u91cf\u662f\u524d\u5e8f\u7247\u6bb5\u5b9a\u4e49\u7684 mapping \u5bf9\u8c61\n",
        "    ordered_dict in some_set\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_set.add(ordered_dict)\n",
        "    len(some_set)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    another_ordered_dict in some_set\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    1\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_set.add(another_ordered_dict)\n",
        "    len(some_set)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    another_set = set()\n",
        "    another_set.add(ordered_dict)\n",
        "    another_ordered_dict in another_set\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    another_set.add(another_ordered_dict)\n",
        "    len(another_set)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    dictionary in another_set\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    another_set.add(another_ordered_dict)\n",
        "    len(another_set)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "    \u56e0\u6b64\uff0c\u4e0d\u4e00\u81f4\u6027\u662f\u7531\u4e8e `another_ordered_dict in another_set` \u7ed3\u679c\u4e3a `False`\u3002 \u56e0\u4e3a `ordered_dict` \u5df2\u7ecf\u5728 `another_set` \u4e2d\uff0c\u4f46\u5982\u524d\u6240\u8ff0\uff0c `ordered_dict == another_ordered_dict` \u7684\u7ed3\u679c\u4e3a `False`\uff0c\u4f1a\u5728\u540e\u7eed\u518d\u52a0\u5165 `another_ordered_dict` \u5230 `another_set` \u4e2d\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Keep trying.../\u4e0d\u505c\u7684try *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_func():\n",
        "    try:\n",
        "        return 'from_try'\n",
        "    finally:\n",
        "        return 'from_finally'\n",
        "\n",
        "def another_func(): \n",
        "    for _ in range(3):\n",
        "        try:\n",
        "            continue\n",
        "        finally:\n",
        "            print(\"Finally!\")\n",
        "\n",
        "def one_more_func(): # A gotcha!\n",
        "    try:\n",
        "        for i in range(3):\n",
        "            try:\n",
        "                1 / i\n",
        "            except ZeroDivisionError:\n",
        "                # Let's throw it here and handle it outside for loop\n",
        "                raise ZeroDivisionError(\"A trivial divide by zero error\")\n",
        "            finally:\n",
        "                print(\"Iteration\", i)\n",
        "                break\n",
        "    except ZeroDivisionError as e:\n",
        "        print(\"Zero division error occurred\", e)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "'from_finally'\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Finally!\n",
              "Finally!\n",
              "Finally!\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "ZeroDivisionError: division by zero\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "1 / 0\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Iteration 0\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "one_more_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u5f53\u5728 \"try...finally\" \u8bed\u53e5\u7684 `try` \u4e2d\u6267\u884c `return`, `break` \u6216 `continue` \u540e, `finally` \u5b50\u53e5\u4f9d\u7136\u4f1a\u6267\u884c.\n",
        "- \u51fd\u6570\u7684\u8fd4\u56de\u503c\u7531\u6700\u540e\u6267\u884c\u7684 `return` \u8bed\u53e5\u51b3\u5b9a. \u7531\u4e8e `finally` \u5b50\u53e5\u4e00\u5b9a\u4f1a\u6267\u884c, \u6240\u4ee5 `finally` \u5b50\u53e5\u4e2d\u7684 `return` \u5c06\u59cb\u7ec8\u662f\u6700\u540e\u6267\u884c\u7684\u8bed\u53e5.\n",
        "- \u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5982\u679c finally \u5b50\u53e5\u6267\u884c `return` \u6216 `break` \u8bed\u53e5\uff0c\u4e34\u65f6\u4fdd\u5b58\u7684\u5f02\u5e38\u5c06\u88ab\u4e22\u5f03\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > For what?/\u4e3a\u4ec0\u4e48?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_string = \"wtf\"\n",
        "some_dict = {}\n",
        "for i, some_dict[i] in enumerate(some_string):\n",
        "    pass\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "{0: 'w', 1: 't', 2: 'f'}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict # \u521b\u5efa\u4e86\u7d22\u5f15\u5b57\u5178.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "####  \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* [Python \u8bed\u6cd5](https://docs.python.org/3/reference/grammar.html) \u4e2d\u5bf9 `for` \u7684\u5b9a\u4e49\u662f:\n",
        "  ```\n",
        "  for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]\n",
        "  ```\n",
        "  \u5176\u4e2d `exprlist` \u6307\u5206\u914d\u76ee\u6807. \u8fd9\u610f\u5473\u7740\u5bf9\u53ef\u8fed\u4ee3\u5bf9\u8c61\u4e2d\u7684**\u6bcf\u4e00\u9879\u90fd\u4f1a\u6267\u884c**\u7c7b\u4f3c `{exprlist} = {next_value}` \u7684\u64cd\u4f5c.\n",
        "\n",
        "  \u4e00\u4e2a\u6709\u8da3\u7684\u4f8b\u5b50\u8bf4\u660e\u4e86\u8fd9\u4e00\u70b9:\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  for i in range(4):\n",
        "      print(i)\n",
        "      i = 10\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **Output:**\n",
        "  ```\n",
        "  0\n",
        "  1\n",
        "  2\n",
        "  3\n",
        "  ```\n",
        "\n",
        "  \u4f60\u53ef\u66fe\u89c9\u5f97\u8fd9\u4e2a\u5faa\u73af\u53ea\u4f1a\u8fd0\u884c\u4e00\u6b21?\n",
        "\n",
        "  **\ud83d\udca1 \u8bf4\u660e:**\n",
        "\n",
        "  - \u7531\u4e8e\u5faa\u73af\u5728Python\u4e2d\u5de5\u4f5c\u65b9\u5f0f, \u8d4b\u503c\u8bed\u53e5 `i = 10` \u5e76\u4e0d\u4f1a\u5f71\u54cd\u8fed\u4ee3\u5faa\u73af, \u5728\u6bcf\u6b21\u8fed\u4ee3\u5f00\u59cb\u4e4b\u524d, \u8fed\u4ee3\u5668(\u8fd9\u91cc\u6307 `range(4)`) \u751f\u6210\u7684\u4e0b\u4e00\u4e2a\u5143\u7d20\u5c31\u88ab\u89e3\u5305\u5e76\u8d4b\u503c\u7ed9\u76ee\u6807\u5217\u8868\u7684\u53d8\u91cf(\u8fd9\u91cc\u6307 `i`)\u4e86.\n",
        "\n",
        "* \u5728\u6bcf\u4e00\u6b21\u7684\u8fed\u4ee3\u4e2d, `enumerate(some_string)` \u51fd\u6570\u5c31\u751f\u6210\u4e00\u4e2a\u65b0\u503c `i` (\u8ba1\u6570\u5668\u589e\u52a0) \u5e76\u4ece `some_string` \u4e2d\u83b7\u53d6\u4e00\u4e2a\u5b57\u7b26. \u7136\u540e\u5c06\u5b57\u5178 `some_dict` \u952e `i` (\u521a\u521a\u5206\u914d\u7684) \u7684\u503c\u8bbe\u4e3a\u8be5\u5b57\u7b26. \u672c\u4f8b\u4e2d\u5faa\u73af\u7684\u5c55\u5f00\u53ef\u4ee5\u7b80\u5316\u4e3a:\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  i, some_dict[i] = (0, 'w')\n",
        "  i, some_dict[i] = (1, 't')\n",
        "  i, some_dict[i] = (2, 'f')\n",
        "  some_dict\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Evaluation time discrepancy/\u6267\u884c\u65f6\u673a\u5dee\u5f02\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "array = [1, 8, 15]\n",
        "# \u4e00\u4e2a\u5178\u578b\u7684\u751f\u6210\u5668\u8868\u8fbe\u5f0f\n",
        "g = (x for x in array if array.count(x) > 0)\n",
        "array = [2, 8, 22]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "[8]\n"
          ]
        }
      ],
      "source": [
        "print(list(g)) #\u5176\u4ed6\u7684\u503c\u53bb\u54ea\u513f\u4e86\uff1f\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "array_1 = [1,2,3,4]\n",
        "g1 = (x for x in array_1)\n",
        "array_1 = [1,2,3,4,5]\n",
        "\n",
        "array_2 = [1,2,3,4]\n",
        "g2 = (x for x in array_2)\n",
        "array_2[:] = [1,2,3,4,5]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "[1,2,3,4]\n",
            "\n"
          ]
        }
      ],
      "source": [
        "print(list(g1))\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "[1,2,3,4,5]\n"
          ]
        }
      ],
      "source": [
        "print(list(g2))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "array_3 = [1, 2, 3]\n",
        "array_4 = [10, 20, 30]\n",
        "gen = (i + j for i in array_3 for j in array_4)\n",
        "\n",
        "array_3 = [4, 5, 6]\n",
        "array_4 = [400, 500, 600]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "[401, 501, 601, 402, 502, 602, 403, 503, 603]\n"
          ]
        }
      ],
      "source": [
        "print(list(gen))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- \u5728[\u751f\u6210\u5668](https://wiki.python.org/moin/Generators)\u8868\u8fbe\u5f0f\u4e2d, `in` \u5b50\u53e5\u5728\u58f0\u660e\u65f6\u6267\u884c, \u800c\u6761\u4ef6\u5b50\u53e5\u5219\u662f\u5728\u8fd0\u884c\u65f6\u6267\u884c.\n",
        "- \u6240\u4ee5\u5728\u8fd0\u884c\u524d, `array` \u5df2\u7ecf\u88ab\u91cd\u65b0\u8d4b\u503c\u4e3a `[2, 8, 22]`, \u56e0\u6b64\u5bf9\u4e8e\u4e4b\u524d\u7684 `1`, `8` \u548c `15`, \u53ea\u6709 `count(8)` \u7684\u7ed3\u679c\u662f\u5927\u4e8e `0` \u7684, \u6240\u4ee5\u751f\u6210\u5668\u53ea\u4f1a\u751f\u6210 `8`.\n",
        "- \u7b2c\u4e8c\u90e8\u5206\u4e2d `g1` \u548c `g2` \u7684\u8f93\u51fa\u5dee\u5f02\u5219\u662f\u7531\u4e8e\u53d8\u91cf `array_1` \u548c `array_2` \u88ab\u91cd\u65b0\u8d4b\u503c\u7684\u65b9\u5f0f\u5bfc\u81f4\u7684.\n",
        "- \u5728\u7b2c\u4e00\u79cd\u60c5\u51b5\u4e0b, `array_1` \u88ab\u7ed1\u5b9a\u5230\u65b0\u5bf9\u8c61 `[1,2,3,4,5]`, \u56e0\u4e3a `in` \u5b50\u53e5\u662f\u5728\u58f0\u660e\u65f6\u88ab\u6267\u884c\u7684\uff0c \u6240\u4ee5\u5b83\u4ecd\u7136\u5f15\u7528\u65e7\u5bf9\u8c61 `[1,2,3,4]`(\u5e76\u6ca1\u6709\u88ab\u9500\u6bc1).\n",
        "- \u5728\u7b2c\u4e8c\u79cd\u60c5\u51b5\u4e0b, \u5bf9 `array_2` \u7684\u5207\u7247\u8d4b\u503c\u5c06\u76f8\u540c\u7684\u65e7\u5bf9\u8c61 `[1,2,3,4]` \u539f\u5730\u66f4\u65b0\u4e3a `[1,2,3,4,5]`. \u56e0\u6b64 `g2` \u548c `array_2` \u4ecd\u7136\u5f15\u7528\u540c\u4e00\u4e2a\u5bf9\u8c61(\u8fd9\u4e2a\u5bf9\u8c61\u73b0\u5728\u5df2\u7ecf\u66f4\u65b0\u4e3a `[1,2,3,4,5]`).\n",
        "- \u597d\u5566\uff0c\u6309\u7167\u76ee\u524d\u8ba8\u8bba\u7684\u903b\u8f91\uff0c\u7b2c\u4e09\u4e2a\u4ee3\u7801\u6bb5\u4e2d\u7684 `list(gen)` \u7684\u503c\u4e0d\u5e94\u8be5\u662f `[11, 21, 31, 12, 22, 32, 13, 23, 33]` \u5417? \uff08\u6bd5\u7adf `array_3` \u548c `array_4` \u7684\u884c\u4e3a\u4e0e `array_1` \u4e00\u6837\uff09\u3002 [PEP-289](https://www.python.org/dev/peps/pep-0289/#the-details) \u4e2d\u89e3\u91ca\u4e86\uff08\u53ea\u6709\uff09`array_4` \u503c\u66f4\u65b0\u7684\u539f\u56e0\n",
        "     > \u53ea\u6709\u6700\u5916\u5c42\u7684 for \u8868\u8fbe\u5f0f\u4f1a\u7acb\u5373\u8ba1\u7b97\uff0c\u5176\u4ed6\u8868\u8fbe\u5f0f\u4f1a\u5ef6\u8fdf\u5230\u751f\u6210\u5668\u8fd0\u884c\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > `is not ...` is not `is (not ...)`/`is not ...` \u4e0d\u662f `is (not ...)`\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'something' is not None\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'something' is (not None)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- `is not` \u662f\u4e2a\u5355\u72ec\u7684\u4e8c\u5143\u8fd0\u7b97\u7b26, \u4e0e\u5206\u522b\u4f7f\u7528 `is` \u548c `not` \u4e0d\u540c.\n",
        "-  \u5982\u679c\u64cd\u4f5c\u7b26\u4e24\u4fa7\u7684\u53d8\u91cf\u6307\u5411\u540c\u4e00\u4e2a\u5bf9\u8c61, \u5219 `is not` \u7684\u7ed3\u679c\u4e3a `False`, \u5426\u5219\u7ed3\u679c\u4e3a `True`.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > A tic-tac-toe where X wins in the first attempt!/\u4e00\u8e74\u5373\u81f3!\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# \u6211\u4eec\u5148\u521d\u59cb\u5316\u4e00\u4e2a\u53d8\u91cfrow\n",
        "row = [\"\"]*3 #row i['', '', '']\n",
        "# \u5e76\u521b\u5efa\u4e00\u4e2a\u53d8\u91cfboard\n",
        "board = [row]*3\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[['', '', ''], ['', '', ''], ['', '', '']]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "board\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['', '', '']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "board[0]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "''\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "board[0][0]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[['X', '', ''], ['X', '', ''], ['X', '', '']]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "board[0][0] = \"X\"\n",
        "board\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u6211\u4eec\u6709\u6ca1\u6709\u8d4b\u503c\u8fc73\u4e2a \"X\" \u5462\uff1f\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "\u5f53\u6211\u4eec\u521d\u59cb\u5316 `row` \u53d8\u91cf\u65f6, \u4e0b\u9762\u8fd9\u5f20\u56fe\u5c55\u793a\u4e86\u5185\u5b58\u4e2d\u7684\u60c5\u51b5\u3002\n",
        "\n",
        "![image](/images/tic-tac-toe/after_row_initialized.png)\n",
        "\n",
        "\u800c\u5f53\u901a\u8fc7\u5bf9 `row` \u505a\u4e58\u6cd5\u6765\u521d\u59cb\u5316 `board` \u65f6, \u5185\u5b58\u4e2d\u7684\u60c5\u51b5\u5219\u5982\u4e0b\u56fe\u6240\u793a (\u6bcf\u4e2a\u5143\u7d20 `board[0]`, `board[1]` \u548c `board[2]` \u90fd\u548c `row` \u4e00\u6837\u5f15\u7528\u4e86\u540c\u4e00\u5217\u8868.)\n",
        "\n",
        "![image](/images/tic-tac-toe/after_board_initialized.png)\n",
        "\n",
        "\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u4e0d\u4f7f\u7528\u53d8\u91cf `row` \u751f\u6210 `board` \u6765\u907f\u514d\u8fd9\u79cd\u60c5\u51b5. ([\u8fd9\u4e2a](https://github.com/satwikkansal/wtfpython/issues/68)issue\u63d0\u51fa\u4e86\u8fd9\u4e2a\u9700\u6c42.)\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[['X', '', ''], ['', '', ''], ['', '', '']]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "board = [['']*3 for _ in range(3)]\n",
        "board[0][0] = \"X\"\n",
        "board\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Schr\u00f6dinger's variable/\u859b\u5b9a\u8c14\u7684\u53d8\u91cf *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "funcs = []\n",
        "results = []\n",
        "for x in range(7):\n",
        "    def some_func():\n",
        "        return x\n",
        "    funcs.append(some_func)\n",
        "    results.append(some_func()) # \u6ce8\u610f\u8fd9\u91cc\u51fd\u6570\u88ab\u6267\u884c\u4e86\n",
        "\n",
        "funcs_results = [func() for func in funcs]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[0, 1, 2, 3, 4, 5, 6]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "results\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[6, 6, 6, 6, 6, 6, 6]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "funcs_results\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5373\u4f7f\u6bcf\u6b21\u5728\u8fed\u4ee3\u4e2d\u5c06 `some_func` \u52a0\u5165 `funcs` \u524d\u7684 `x` \u503c\u90fd\u4e0d\u76f8\u540c, \u6240\u6709\u7684\u51fd\u6570\u8fd8\u662f\u90fd\u8fd4\u56de6.\n",
        "\n",
        "// \u518d\u6362\u4e2a\u4f8b\u5b50\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[512, 512, 512, 512, 512, 512, 512, 512, 512, 512]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "powers_of_x = [lambda x: x**i for i in range(10)]\n",
        "[f(2) for f in powers_of_x]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u5f53\u5728\u5faa\u73af\u5185\u90e8\u5b9a\u4e49\u4e00\u4e2a\u51fd\u6570\u65f6, \u5982\u679c\u8be5\u51fd\u6570\u5728\u5176\u4e3b\u4f53\u4e2d\u4f7f\u7528\u4e86\u5faa\u73af\u53d8\u91cf, \u5219\u95ed\u5305\u51fd\u6570\u5c06\u4e0e\u5faa\u73af\u53d8\u91cf\u7ed1\u5b9a, \u800c\u4e0d\u662f\u5b83\u7684\u503c. \u56e0\u6b64, \u6240\u6709\u7684\u51fd\u6570\u90fd\u662f\u4f7f\u7528\u6700\u540e\u5206\u914d\u7ed9\u53d8\u91cf\u7684\u503c\u6765\u8fdb\u884c\u8ba1\u7b97\u7684.\n",
        "\n",
        "- \u53ef\u4ee5\u901a\u8fc7\u5c06\u5faa\u73af\u53d8\u91cf\u4f5c\u4e3a\u547d\u540d\u53d8\u91cf\u4f20\u9012\u7ed9\u51fd\u6570\u6765\u83b7\u5f97\u9884\u671f\u7684\u7ed3\u679c. **\u4e3a\u4ec0\u4e48\u8fd9\u6837\u53ef\u884c?** \u56e0\u4e3a\u8fd9\u4f1a\u5728\u51fd\u6570\u5185\u518d\u6b21\u5b9a\u4e49\u4e00\u4e2a\u5c40\u90e8\u53d8\u91cf\u3002\u6211\u4eec\u53ef\u4ee5\u770b\u5230\u5b83\u4f7f\u7528\u4e86\u6765\u81ea\u4e0a\u4e0b\u6587\u7684`x`\uff08\u5373*\u4e0d\u662f*\u5c40\u90e8\u53d8\u91cf\uff09\uff1a\n",
        "\uff08\u8bd1\u8005\u6ce8: inspect\u4f4d\u4e8ePython\u6807\u51c6\u5e93\u4e2d\uff0c\u8be5\u6a21\u5757\u7528\u4e8e\u6536\u96c6python\u5bf9\u8c61\u7684\u4fe1\u606f\uff0c\u53ef\u4ee5\u83b7\u53d6\u7c7b\u6216\u51fd\u6570\u7684\u53c2\u6570\u7684\u4fe1\u606f\uff0c\u6e90\u7801\uff0c\u89e3\u6790\u5806\u6808\uff0c\u5bf9\u5bf9\u8c61\u8fdb\u884c\u7c7b\u578b\u68c0\u67e5\u7b49\u7b49\uff0cPython3.3+\u7248\u672c\u652f\u6301getclosurevars\u51fd\u6570\uff09\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "ClosureVars(nonlocals={}, globals={'x': 6}, builtins={}, unbound=set())\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import inspect\n",
        "inspect.getclosurevars(funcs[0])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u7531\u4e8e `x` \u662f\u4e00\u4e2a\u5168\u5c40\u503c\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u66f4\u65b0 `x` \u6765\u66f4\u6539 `funcs` \u7528\u6765\u67e5\u627e\u548c\u8fd4\u56de\u7684\u503c\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[42, 42, 42, 42, 42, 42, 42]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = 42\n",
        "[func() for func in funcs]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u8981\u83b7\u5f97\u60f3\u8981\u7684\u7ed3\u679c\uff0c\u60a8\u53ef\u4ee5\u5c06\u5faa\u73af\u53d8\u91cf\u4f5c\u4e3a\u547d\u540d\u53d8\u91cf\u4f20\u9012\u7ed9\u51fd\u6570\u3002 **\u4e3a\u4ec0\u4e48\u4f1a\u8fd9\u6837\uff1f** \u56e0\u4e3a\u8fd9\u4f1a\u5728\u51fd\u6570\u7684\u4f5c\u7528\u57df\u5185\u5b9a\u4e49\u53d8\u91cf\u3002 \u5b83\u5c06\u4e0d\u518d\u8fdb\u5165\u5468\u56f4\uff08\u5168\u5c40\uff09\u8303\u56f4\u6765\u67e5\u627e\u53d8\u91cf\u503c\uff0c\u800c\u662f\u4f1a\u521b\u5efa\u4e00\u4e2a\u5c40\u90e8\u53d8\u91cf\u6765\u5b58\u50a8\u8be5\u65f6\u95f4\u70b9\u7684\u201cx\u201d\u503c\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "funcs = []\n",
        "for x in range(7):\n",
        "    def some_func(x=x):\n",
        "        return x\n",
        "    funcs.append(some_func)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[0, 1, 2, 3, 4, 5, 6]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "funcs_results = [func() for func in funcs]\n",
        "funcs_results\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u6b64\u65f6\uff0c\u4e0d\u518d\u4f7f\u7528\u5168\u5c40\u53d8\u91cf `x`\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "ClosureVars(nonlocals={}, globals={}, builtins={}, unbound=set())\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "inspect.getclosurevars(funcs[0])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > The chicken-egg problem/\u5148\u6709\u9e21\u8fd8\u662f\u5148\u6709\u86cb *\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "isinstance(3, int)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "isinstance(type, object)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "isinstance(object, type)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\u90a3\u4e48\u5230\u5e95\u8c01\u662f\u201c\u6700\u7ec8\u201d\u7684\u57fa\u7c7b\u5462\uff1f\u4e0b\u8fb9\u987a\u4fbf\u5217\u51fa\u66f4\u591a\u7684\u4ee4\u4eba\u56f0\u60d1\u7684\u5730\u65b9\n",
        "\n",
        "2\\. \n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class A: pass\n",
        "isinstance(A, A)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "isinstance(type, type)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "isinstance(object, object)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "issubclass(int, object)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "issubclass(type, object)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "issubclass(object, type)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- `type` \u662f Python \u4e2d\u7684[\u5143\u7c7b](https://realpython.com/python-metaclasses/)\u3002\n",
        "- Python \u4e2d\uff0c**\u4e00\u5207**\u7686\u5bf9\u8c61\uff0c\u5176\u4e2d\u5305\u62ec\u7c7b\u53ca\u5176\u5bf9\u8c61\uff08\u5b9e\u4f8b\uff09\u3002\n",
        "- `type` \u7c7b\u578b\u662f`object`\u7c7b\u7684\u5143\u7c7b\uff0c\u6bcf\u4e2a\u7c7b\uff08\u5305\u62ec`type`\uff09\u90fd\u76f4\u63a5\u6216\u95f4\u63a5\u5730\u7ee7\u627f\u81ea`object`\u3002\n",
        "- \u5bf9\u8c61\u548c\u7c7b\u578b\u4e4b\u95f4\u6ca1\u6709\u771f\u6b63\u7684\u57fa\u7c7b\u3002\u4e0a\u8ff0\u7247\u6bb5\u4e2d\u7684\u4ee4\u4eba\u56f0\u60d1\u7684\u5730\u65b9\u4e4b\u6240\u4ee5\u51fa\u73b0\uff0c\u662f\u56e0\u4e3a\u6211\u4eec\u4ece Python \u7c7b\u7684\u89d2\u5ea6\u8003\u8651\u8fd9\u4e9b\u5173\u7cfb\uff08issubclass \u548c isinstance\uff09\u3002 `object`\u548c`type`\u4e4b\u95f4\u7684\u5173\u7cfb\u4e0d\u80fd\u5728\u7eafpython\u4e2d\u91cd\u73b0\u3002 \u66f4\u51c6\u786e\u5730\u8bf4\uff0c\u4ee5\u4e0b\u5173\u7cfb\u4e0d\u80fd\u5728\u7eaf Python \u4e2d\u91cd\u73b0:\n",
        "    + A\u7c7b\u662fB\u7c7b\u7684\u4e00\u4e2a\u5b9e\u4f8b\uff0cB\u7c7b\u662fA\u7c7b\u7684\u4e00\u4e2a\u5b9e\u4f8b\u3002\n",
        "    + A\u7c7b\u662f\u5b83\u81ea\u5df1\u7684\u4e00\u4e2a\u5b9e\u4f8b\u3002\n",
        "- `object`\u548c`type`\u4e4b\u95f4\u7684\u5173\u7cfb\uff08\u65e2\u662f\u5f7c\u6b64\u7684\u5b9e\u4f8b\uff0c\u4e5f\u662f\u5b83\u4eec\u81ea\u5df1\u7684\u5b9e\u4f8b\uff09\u5b58\u5728\u4e8e Python \u4e2d\uff0c\u8fd9\u662f\u6e90\u4e8e\u5b9e\u73b0\u5c42\u7ea7\u4e0a\u7684\u201c\u4f5c\u5f0a\u201d\u884c\u4e3a\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Subclass relationships/\u5b50\u7c7b\u5173\u7cfb *\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "from collections import Hashable\n",
        "issubclass(list, object)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "issubclass(object, Hashable)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "issubclass(list, Hashable)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5b50\u7c7b\u5173\u7cfb\u5e94\u8be5\u662f\u53ef\u4f20\u9012\u7684, \u5bf9\u5427? (\u5373, \u5982\u679c `A` \u662f `B` \u7684\u5b50\u7c7b, `B` \u662f `C` \u7684\u5b50\u7c7b, \u90a3\u4e48 `A` _\u5e94\u8be5_ \u662f `C` \u7684\u5b50\u7c7b.)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* Python \u4e2d\u7684\u5b50\u7c7b\u5173\u7cfb\u5e76\u4e0d\u4e00\u5b9a\u662f\u4f20\u9012\u7684. \u4efb\u4f55\u4eba\u90fd\u53ef\u4ee5\u5728\u5143\u7c7b\u4e2d\u968f\u610f\u5b9a\u4e49 `__subclasscheck__`.\n",
        "* \u5f53 `issubclass(cls, Hashable)` \u88ab\u8c03\u7528\u65f6, \u5b83\u53ea\u662f\u5728 `cls` \u4e2d\u5bfb\u627e `__hash__` \u65b9\u6cd5\u6216\u8005\u4ece\u7ee7\u627f\u7684\u7236\u7c7b\u4e2d\u5bfb\u627e `__hash__` \u65b9\u6cd5.\n",
        "* \u7531\u4e8e `object` is \u53ef\u6563\u5217\u7684(hashable), \u4f46\u662f `list` \u662f\u4e0d\u53ef\u6563\u5217\u7684, \u6240\u4ee5\u5b83\u6253\u7834\u4e86\u8fd9\u79cd\u4f20\u9012\u5173\u7cfb.\n",
        "* \u5728[\u8fd9\u91cc](https://www.naftaliharris.com/blog/python-subclass-intransitivity/)\u53ef\u4ee5\u627e\u5230\u66f4\u8be6\u7ec6\u7684\u89e3\u91ca.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Methods equality and identity/\u65b9\u6cd5\u7684\u76f8\u7b49\u6027\u548c\u552f\u4e00\u6027 *\n",
        "1.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class SomeClass:\n",
        "    def method(self):\n",
        "        pass\n",
        "\n",
        "    @classmethod\n",
        "    def classm(cls):\n",
        "        pass\n",
        "\n",
        "    @staticmethod\n",
        "    def staticm():\n",
        "        pass\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(SomeClass.method is SomeClass.method)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "False\n"
          ]
        }
      ],
      "source": [
        "print(SomeClass.classm is SomeClass.classm)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(SomeClass.classm == SomeClass.classm)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(SomeClass.staticm is SomeClass.staticm)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\u8bbf\u95ee `classm` \u4e24\u6b21\uff0c\u6211\u4eec\u5f97\u5230\u4e00\u4e2a\u76f8\u7b49\u7684\u5bf9\u8c61\uff0c\u4f46\u4e0d\u662f*\u540c\u4e00\u4e2a*\uff1f \u8ba9\u6211\u4eec\u770b\u770b `SomeClass` \u7684\u5b9e\u4f8b\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1a\n",
        "\n",
        "2.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1 = SomeClass()\n",
        "o2 = SomeClass()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "False\n"
          ]
        }
      ],
      "source": [
        "print(o1.method == o2.method)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(o1.method == o1.method)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "False\n"
          ]
        }
      ],
      "source": [
        "print(o1.method is o1.method)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "False\n"
          ]
        }
      ],
      "source": [
        "print(o1.classm is o1.classm)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(o1.classm == o1.classm == o2.classm == SomeClass.classm)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "True\n"
          ]
        }
      ],
      "source": [
        "print(o1.staticm is o1.staticm is o2.staticm is SomeClass.staticm)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8bbf\u95ee ` classm` or `method` \u4e24\u6b21, \u4e3a `SomeClass` \u7684\u540c\u4e00\u4e2a\u5b9e\u4f8b\u521b\u5efa\u4e86\u76f8\u7b49\u4f46\u662f*\u4e0d\u540c*\u7684\u5bf9\u8c61\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "* \u51fd\u6570\u662f[\u63cf\u8ff0\u7b26](https://docs.python.org/3/howto/descriptor.html)\u3002\u6bcf\u5f53\u5c06\u51fd\u6570\u4f5c\u4e3a\u5c5e\u6027\u8bbf\u95ee\u65f6\uff0c\u5c31\u4f1a\u8c03\u7528\u63cf\u8ff0\u7b26\uff0c\u521b\u5efa\u4e00\u4e2a\u65b9\u6cd5\u5bf9\u8c61\uff0c\u8be5\u5bf9\u8c61\u5c06\u51fd\u6570\u4e0e\u62e5\u6709\u8be5\u5c5e\u6027\u7684\u5bf9\u8c61\u201c\u7ed1\u5b9a\u201d\u3002\u5982\u679c\u88ab\u8c03\u7528\uff0c\u8be5\u65b9\u6cd5\u8c03\u7528\u51fd\u6570\uff0c\u9690\u5f0f\u4f20\u9012\u7ed1\u5b9a\u5bf9\u8c61\u4f5c\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\uff08\u8fd9\u5c31\u662f\u6211\u4eec\u5982\u4f55\u5c06 self \u4f5c\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\u83b7\u53d6\uff0c\u5c3d\u7ba1\u6ca1\u6709\u663e\u5f0f\u4f20\u9012\u5b83\uff09\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<bound method SomeClass.method of <__main__.SomeClass object at ...>>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1.method\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u591a\u6b21\u8bbf\u95ee\u8be5\u5c5e\u6027\uff0c\u6bcf\u6b21\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b9\u6cd5\u5bf9\u8c61\uff01 \u56e0\u6b64\uff0c`o1.method is o1.method` \u6c38\u8fdc\u4e0d\u4f1a\u662f\u771f\u7684\u3002\u4f46\u662f\uff0c\u5c06\u51fd\u6570\u4f5c\u4e3a\u7c7b\u5c5e\u6027\uff08\u800c\u4e0d\u662f\u5b9e\u4f8b\uff09\u8bbf\u95ee\u5e76\u4e0d\u4f1a\u521b\u5efa\u65b9\u6cd5\u5bf9\u8c61\uff0c\u6240\u4ee5 `SomeClass.method is SomeClass.method` \u662f\u771f\u7684\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<function SomeClass.method at ...>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeClass.method\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* `classmethod` \u5c06\u51fd\u6570\u8f6c\u6362\u4e3a\u7c7b\u65b9\u6cd5\u3002 \u7c7b\u65b9\u6cd5\u662f\u63cf\u8ff0\u7b26\uff0c\u5f53\u88ab\u8bbf\u95ee\u65f6\uff0c\u5b83\u4f1a\u521b\u5efa\u4e00\u4e2a\u7ed1\u5b9a*\u7c7b\u672c\u8eab*\u7684\u65b9\u6cd5\u5bf9\u8c61\uff0c\u800c\u4e0d\u662f\u5bf9\u8c61\u672c\u8eab\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<bound method SomeClass.classm of <class '__main__.SomeClass'>>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1.classm\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u4e0e\u51fd\u6570\u4e0d\u540c\uff0c`classmethod` \u5728\u4f5c\u4e3a\u7c7b\u5c5e\u6027\u8bbf\u95ee\u65f6\u4e5f\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b9\u6cd5\uff08\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u5b83\u4eec\u7ed1\u5b9a\u7c7b\uff0c\u800c\u4e0d\u662f\u7c7b\u7684\u7c7b\u578b\uff09\u3002 \u6240\u4ee5 `SomeClass.classm is SomeClass.classm` \u662f\u5047\u7684\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<bound method SomeClass.classm of <class '__main__.SomeClass'>>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeClass.classm\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5f53\u4e24\u4e2a\u51fd\u6570\u76f8\u7b49\u5e76\u4e14\u7ed1\u5b9a\u7684\u5bf9\u8c61\u76f8\u540c\u65f6\uff0c\u65b9\u6cd5\u5bf9\u8c61\u6bd4\u8f83\u76f8\u7b49\u3002 \u6240\u4ee5`o1.method == o1.method` \u4e3a\u771f\uff0c\u5c3d\u7ba1\u5b83\u4eec\u5728\u5185\u5b58\u4e2d\u662f\u4e24\u4e2a\u4e0d\u540c\u7684\u5bf9\u8c61\u3002\n",
        "* `staticmethod` \u5c06\u51fd\u6570\u8f6c\u6362\u4e3a\u201c\u65e0\u64cd\u4f5c\u201d\u63cf\u8ff0\u7b26\uff0c\u5b83\u6309\u539f\u6837\u8fd4\u56de\u51fd\u6570\u3002\u6ca1\u6709\u65b9\u6cd5\u5bf9\u8c61\u88ab\u521b\u5efa\uff0c\u6240\u4ee5 `is` \u7684\u6bd4\u8f83\u8fd0\u7b97\u4e3a\u771f\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<function SomeClass.staticm at ...>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1.staticm\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<function SomeClass.staticm at ...>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeClass.staticm\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u6bcf\u6b21 Python \u8c03\u7528\u5b9e\u4f8b\u65b9\u6cd5\u65f6\u90fd\u5fc5\u987b\u521b\u5efa\u65b0\u7684\u201c\u65b9\u6cd5\u201d\u5bf9\u8c61\uff0c\u5e76\u4e14\u6bcf\u6b21\u90fd\u5fc5\u987b\u4fee\u6539\u53c2\u6570\u4ee5\u63d2\u5165 `self` \u4e25\u91cd\u5f71\u54cd\u6027\u80fd\u3002CPython 3.7 [\u89e3\u51b3\u4e86\u8fd9\u4e2a\u95ee\u9898](https://bugs.python.org/issue26110) \u3002\u901a\u8fc7\u5f15\u5165\u65b0\u7684\u64cd\u4f5c\u7801\u6765\u5904\u7406\u8c03\u7528\u65b9\u6cd5\u800c\u4e0d\u521b\u5efa\u4e34\u65f6\u65b9\u6cd5\u5bf9\u8c61\u3002\u8fd9\u4ec5\u5728\u5b9e\u9645\u8c03\u7528\u8bbf\u95ee\u7684\u51fd\u6570\u65f6\u4f7f\u7528\uff0c\u56e0\u6b64\u8fd9\u91cc\u7684\u4ee3\u7801\u7247\u6bb5\u4e0d\u53d7\u5f71\u54cd\uff0c\u4ecd\u7136\u4f1a\u751f\u6210\u65b9\u6cd5:)\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > All-true-ation/\u8fd4\u56deTrue\u7684all\u51fd\u6570 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "all([True, True, True])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "all([True, True, False])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "all([])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "all([[]])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "all([[[]]])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4e3a\u4ec0\u4e48\u4f1a\u6709\u8fd9\u79cdTrue-False\u7684\u53d8\u5316\uff1f\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- `all` \u51fd\u6570\u7684\u5b9e\u73b0\u7b49\u4ef7\u4e8e\uff1a\n",
        "\n",
        "- ```py\n",
        "  def all(iterable):\n",
        "      for element in iterable:\n",
        "          if not element:\n",
        "              return False\n",
        "      return True\n",
        "  ```\n",
        "\n",
        "- `all([])` \u8fd4\u56de `True` \u56e0\u4e3a\u53ef\u8fed\u4ee3\u5bf9\u8c61\u4e3a\u7a7a\u3002 \n",
        "- `all([[]])` \u8fd4\u56de `False` \u56e0\u4e3a\u4f20\u5165\u7684\u6570\u7ec4\u6709\u4e00\u4e2a\u5143\u7d20 `[]`\uff0c \u5728Python\u4e2d\uff0c\u7a7a\u5217\u8868\u4e3a\u5047\u3002\n",
        "- `all([[[]]])` \u548c\u66f4\u9ad8\u7684\u9012\u5f52\u53d8\u4f53\u603b\u662f`True`\u3002 \u8fd9\u662f\u56e0\u4e3a\u4f20\u9012\u7684\u6570\u7ec4\u7684\u5355\u4e2a\u5143\u7d20\uff08`[[...]]`\uff09\u4e0d\u518d\u662f\u7a7a\u7684\uff0c\u800c\u6709\u503c\u7684\u5217\u8868\u4e3a\u771f\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > The surprising comma/\u610f\u5916\u7684\u9017\u53f7\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  File \"<stdin>\", line 1\n",
              "    def h(x, **kwargs,):\n",
              "                     ^\n",
              "SyntaxError: invalid syntax\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def f(x, y,):\n",
        "     print(x, y)\n",
        "\n",
        "def g(x=4, y=5,):\n",
        "     print(x, y)\n",
        "\n",
        "def h(x, **kwargs,):\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  File \"<stdin>\", line 1\n",
              "    def h(*args,):\n",
              "                ^\n",
              "SyntaxError: invalid syntax\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def h(*args,):\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u5728Python\u51fd\u6570\u7684\u5f62\u5f0f\u53c2\u6570\u5217\u8868\u4e2d, \u5c3e\u968f\u9017\u53f7\u5e76\u4e0d\u4e00\u5b9a\u662f\u5408\u6cd5\u7684.\n",
        "- \u5728Python\u4e2d, \u53c2\u6570\u5217\u8868\u90e8\u5206\u7528\u524d\u7f6e\u9017\u53f7\u5b9a\u4e49, \u90e8\u5206\u7528\u5c3e\u968f\u9017\u53f7\u5b9a\u4e49. \u8fd9\u79cd\u51b2\u7a81\u5bfc\u81f4\u9017\u53f7\u88ab\u5939\u5728\u4e2d\u95f4, \u6ca1\u6709\u89c4\u5219\u5b9a\u4e49\u5b83.(\u8bd1:\u8fd9\u4e00\u53e5\u770b\u5f97\u6211\u4e5f\u5f88\u61f5\u903c,\u53ea\u80fd\u5f3a\u7ffb\u4e86.\u8be6\u7ec6\u89e3\u91ca\u770b\u4e0b\u9762\u7684\u8ba8\u8bba\u5e16\u4f1a\u4e00\u76ee\u4e86\u7136.)\n",
        "- **\u6ce8\u610f:** \u5c3e\u968f\u9017\u53f7\u7684\u95ee\u9898\u5df2\u7ecf\u5728Python 3.6\u4e2d\u88ab[\u4fee\u590d](https://bugs.python.org/issue9232)\u4e86. \u800c\u8fd9\u7bc7[\u5e16\u5b50](https://bugs.python.org/issue9232#msg248399)\u4e2d\u5219\u7b80\u8981\u8ba8\u8bba\u4e86Python\u4e2d\u5c3e\u968f\u9017\u53f7\u7684\u4e0d\u540c\u7528\u6cd5.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Strings and the backslashes/\u5b57\u7b26\u4e32\u4e0e\u53cd\u659c\u6760\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "\"\n",
            "\n"
          ]
        }
      ],
      "source": [
        "print(\"\\\"\")\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "\\\"\n",
            "\n"
          ]
        }
      ],
      "source": [
        "print(r\"\\\"\")\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "File \"<stdin>\", line 1\n",
            "    print(r\"\\\")\n",
            "              ^\n",
            "SyntaxError: EOL while scanning string literal\n",
            "\n"
          ]
        }
      ],
      "source": [
        "print(r\"\\\")\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "r'\\'' == \"\\\\'\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u5728\u4e00\u822c\u7684python\u5b57\u7b26\u4e32\u4e2d\uff0c\u53cd\u659c\u6760\u7528\u4e8e\u8f6c\u4e49\u53ef\u80fd\u5177\u6709\u7279\u6b8a\u542b\u4e49\u7684\u5b57\u7b26\uff08\u5982\u5355\u5f15\u53f7\u3001\u53cc\u5f15\u53f7\u548c\u53cd\u659c\u6760\u672c\u8eab\uff09\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    'wt\"f'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    \"wt\\\"f\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u5728\u4ee5 `r` \u5f00\u5934\u7684\u539f\u59cb\u5b57\u7b26\u4e32\u4e2d, \u53cd\u659c\u6760\u5e76\u6ca1\u6709\u7279\u6b8a\u542b\u4e49.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    r'wt\\\"f' == 'wt\\\\\"f'\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    'wt\\\\\"f'\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    print(repr(r'wt\\\"f')\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    print(\"\\n\")\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    '\\\\n'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    print(r\"\\\\n\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u8fd9\u610f\u5473\u7740\u5f53\u89e3\u6790\u5668\u5728\u539f\u59cb\u5b57\u7b26\u4e32\u4e2d\u9047\u5230\u53cd\u659c\u6760\u65f6\uff0c\u5b83\u671f\u671b\u540e\u9762\u6709\u53e6\u4e00\u4e2a\u5b57\u7b26\u3002 \u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d\uff08`print(r\"\\\")`\uff09\uff0c\u53cd\u659c\u6760\u8f6c\u4e49\u4e86\u5c3e\u968f\u5f15\u53f7\uff0c\u4f7f\u89e3\u6790\u5668\u6ca1\u6709\u7ec8\u6b62\u5f15\u53f7\uff08\u56e0\u6b64\u4ea7\u751f\u4e86`SyntaxError`\uff09\u3002 \u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48\u53cd\u659c\u6760\u5728\u539f\u59cb\u5b57\u7b26\u4e32\u672b\u5c3e\u4e0d\u8d77\u4f5c\u7528\u7684\u539f\u56e0\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > not knot!/\u522b\u7ea0\u7ed3!\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = True\n",
        "y = False\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "not x == y\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  File \"<input>\", line 1\n",
              "    x == not y\n",
              "           ^\n",
              "SyntaxError: invalid syntax\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x == not y\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u8fd0\u7b97\u7b26\u7684\u4f18\u5148\u7ea7\u4f1a\u5f71\u54cd\u8868\u8fbe\u5f0f\u7684\u6c42\u503c\u987a\u5e8f, \u800c\u5728 Python \u4e2d `==` \u8fd0\u7b97\u7b26\u7684\u4f18\u5148\u7ea7\u8981\u9ad8\u4e8e `not` \u8fd0\u7b97\u7b26.\n",
        "* \u6240\u4ee5 `not x == y` \u76f8\u5f53\u4e8e `not (x == y)`, \u540c\u65f6\u7b49\u4ef7\u4e8e `not (True == False)`, \u6700\u540e\u7684\u8fd0\u7b97\u7ed3\u679c\u5c31\u662f `True`.\n",
        "* \u4e4b\u6240\u4ee5 `x == not y` \u4f1a\u629b\u4e00\u4e2a `SyntaxError` \u5f02\u5e38, \u662f\u56e0\u4e3a\u5b83\u4f1a\u88ab\u8ba4\u4e3a\u7b49\u4ef7\u4e8e `(x == not) y`, \u800c\u4e0d\u662f\u4f60\u4e00\u5f00\u59cb\u671f\u671b\u7684 `x == (not y)`.\n",
        "* \u89e3\u91ca\u5668\u671f\u671b `not` \u6807\u8bb0\u662f `not in` \u64cd\u4f5c\u7b26\u7684\u4e00\u90e8\u5206 (\u56e0\u4e3a `==` \u548c `not in` \u64cd\u4f5c\u7b26\u5177\u6709\u76f8\u540c\u7684\u4f18\u5148\u7ea7), \u4f46\u662f\u5b83\u5728 `not` \u6807\u8bb0\u540e\u9762\u627e\u4e0d\u5230 `in` \u6807\u8bb0, \u6240\u4ee5\u4f1a\u629b\u51fa `SyntaxError` \u5f02\u5e38.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Half triple-quoted strings/\u4e09\u4e2a\u5f15\u53f7\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "wtfpython\n"
          ]
        }
      ],
      "source": [
        "print('wtfpython''')\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "wtfpython\n"
          ]
        }
      ],
      "source": [
        "print(\"wtfpython\"\"\")\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# \u4e0b\u9762\u7684\u8bed\u53e5\u4f1a\u629b\u51fa `SyntaxError` \u5f02\u5e38\n",
        "# print('''wtfpython')\n",
        "# print(\"\"\"wtfpython\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "+ Python \u63d0\u4f9b\u9690\u5f0f\u7684[\u5b57\u7b26\u4e32\u8fde\u63a5](https://docs.python.org/2/reference/lexical_analysis.html#string-literal-concatenation), \u4f8b\u5982,\n",
        "  ```\n",
        "  >>> print(\"wtf\" \"python\")\n",
        "  wtfpython\n",
        "  >>> print(\"wtf\" \"\") # or \"wtf\"\"\"\n",
        "  wtf\n",
        "  ```\n",
        "+ `'''` \u548c `\"\"\"` \u5728 Python\u4e2d\u4e5f\u662f\u5b57\u7b26\u4e32\u5b9a\u754c\u7b26, Python \u89e3\u91ca\u5668\u5728\u5148\u9047\u5230\u4e09\u4e2a\u5f15\u53f7\u7684\u7684\u65f6\u5019\u4f1a\u5c1d\u8bd5\u518d\u5bfb\u627e\u4e09\u4e2a\u7ec8\u6b62\u5f15\u53f7\u4f5c\u4e3a\u5b9a\u754c\u7b26, \u5982\u679c\u4e0d\u5b58\u5728\u5219\u4f1a\u5bfc\u81f4 `SyntaxError` \u5f02\u5e38.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > What's wrong with booleans?/\u5e03\u5c14\u4f60\u548b\u4e86?\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# \u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50, \u7edf\u8ba1\u4e0b\u9762\u53ef\u8fed\u4ee3\u5bf9\u8c61\u4e2d\u7684\u5e03\u5c14\u578b\u503c\u7684\u4e2a\u6570\u548c\u6574\u578b\u503c\u7684\u4e2a\u6570\n",
        "mixed_list = [False, 1.0, \"some_string\", 3, True, [], False]\n",
        "integers_found_so_far = 0\n",
        "booleans_found_so_far = 0\n",
        "\n",
        "for item in mixed_list:\n",
        "    if isinstance(item, int):\n",
        "        integers_found_so_far += 1\n",
        "    elif isinstance(item, bool):\n",
        "        booleans_found_so_far += 1\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "4\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "integers_found_so_far\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "booleans_found_so_far\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "'wtf'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_bool = True\n",
        "\"wtf\" * some_bool\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "''\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_bool = False\n",
        "\"wtf\" * some_bool\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def tell_truth():\n",
        "    True = False\n",
        "    if True == False:\n",
        "        print(\"I have lost faith in truth!\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (< 3.x):**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "I have lost faith in truth!\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "tell_truth()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5e03\u5c14\u503c\u662f `int` \u7684\u5b50\u7c7b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    issubclass(bool, int)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    issubclass(int, bool)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u56e0\u6b64\uff0c`True` \u548c `False` \u662f `int` \u7684\u5b9e\u4f8b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  isinstance(True, int)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  isinstance(False, int)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "*  `True` \u7684\u6574\u6570\u503c\u662f `1`, \u800c `False` \u7684\u6574\u6570\u503c\u662f `0`\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  int(True)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  int(False)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5173\u4e8e\u5176\u80cc\u540e\u7684\u539f\u7406, \u8bf7\u770b\u8fd9\u4e2a StackOverflow \u7684[\u56de\u7b54](https://stackoverflow.com/a/8169049/4354153).\n",
        "\n",
        "* \u6700\u521d\uff0cPython \u6ca1\u6709 `bool` \u7c7b\u578b\uff08\u4eba\u4eec\u4f7f\u7528 0 \u8868\u793a\u5047\uff0c\u4f7f\u7528\u975e\u96f6\u503c\uff0c\u5982 1 \u8868\u793a\u771f\uff09\u3002`True`\u3001`False` \u548c `bool` \u7c7b\u578b\u5728 2.x \u7248\u672c\u4e2d\u88ab\u6dfb\u52a0\uff0c\u4f46\u4e3a\u4e86\u5411\u540e\u517c\u5bb9\uff0c`True` \u548c `False` \u4e0d\u80fd\u6210\u4e3a\u5e38\u91cf\u3002\u5b83\u4eec\u53ea\u662f\u5185\u7f6e\u53d8\u91cf\uff0c\u53ef\u4ee5\u91cd\u65b0\u5206\u914d\u5b83\u4eec\n",
        "\n",
        "* Python 3 \u5411\u540e\u4e0d\u517c\u5bb9\uff0c\u95ee\u9898\u7ec8\u4e8e\u5f97\u5230\u89e3\u51b3\uff0c\u56e0\u6b64\u6700\u540e\u4e00\u4e2a\u4ee3\u7801\u6bb5\u4e0d\u9002\u7528\u4e8e Python 3.x\uff01\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Class attributes and instance attributes/\u7c7b\u5c5e\u6027\u548c\u5b9e\u4f8b\u5c5e\u6027\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class A:\n",
        "    x = 1\n",
        "\n",
        "class B(A):\n",
        "    pass\n",
        "\n",
        "class C(A):\n",
        "    pass\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "(1, 1, 1)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "A.x, B.x, C.x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "(1, 2, 1)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "B.x = 2\n",
        "A.x, B.x, C.x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "(3, 2, 3)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "A.x = 3\n",
        "A.x, B.x, C.x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "(3, 3)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = A()\n",
        "a.x, A.x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "(4, 3)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a.x += 1\n",
        "a.x, A.x\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class SomeClass:\n",
        "    some_var = 15\n",
        "    some_list = [5]\n",
        "    another_list = [5]\n",
        "    def __init__(self, x):\n",
        "        self.some_var = x + 1\n",
        "        self.some_list = self.some_list + [x]\n",
        "        self.another_list += [x]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[5, 420]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_obj = SomeClass(420)\n",
        "some_obj.some_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[5, 420]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_obj.another_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[5, 111]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_obj = SomeClass(111)\n",
        "another_obj.some_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[5, 420, 111]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_obj.another_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_obj.another_list is SomeClass.another_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_obj.another_list is some_obj.another_list\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u7c7b\u53d8\u91cf\u548c\u5b9e\u4f8b\u53d8\u91cf\u5728\u5185\u90e8\u662f\u901a\u8fc7\u7c7b\u5bf9\u8c61\u7684\u5b57\u5178\u6765\u5904\u7406(\u8bd1: \u5c31\u662f `__dict__` \u5c5e\u6027). \u5982\u679c\u5728\u5f53\u524d\u7c7b\u7684\u5b57\u5178\u4e2d\u627e\u4e0d\u5230\u7684\u8bdd\u5c31\u53bb\u5b83\u7684\u7236\u7c7b\u4e2d\u5bfb\u627e.\n",
        "* `+=` \u8fd0\u7b97\u7b26\u4f1a\u5728\u539f\u5730\u4fee\u6539\u53ef\u53d8\u5bf9\u8c61, \u800c\u4e0d\u662f\u521b\u5efa\u65b0\u5bf9\u8c61. \u56e0\u6b64, \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b, \u4fee\u6539\u4e00\u4e2a\u5b9e\u4f8b\u7684\u5c5e\u6027\u4f1a\u5f71\u54cd\u5176\u4ed6\u5b9e\u4f8b\u548c\u7c7b\u5c5e\u6027.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > yielding None/\u751f\u6210 None\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_iterable = ('a', 'b')\n",
        "\n",
        "def some_func(val):\n",
        "    return \"something\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a', 'b']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "[x for x in some_iterable]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<generator object <listcomp> at 0x7f70b0a4ad58>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "[(yield x) for x in some_iterable]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a', 'b']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list([(yield x) for x in some_iterable])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a', None, 'b', None]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list((yield x) for x in some_iterable)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a', 'something', 'b', 'something']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list(some_func((yield x)) for x in some_iterable)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u6765\u6e90\u548c\u89e3\u91ca\u53ef\u4ee5\u5728\u8fd9\u91cc\u627e\u5230: https://stackoverflow.com/questions/32139885/yield-in-list-comprehensions-and-generator-expressions\n",
        "- \u76f8\u5173\u9519\u8bef\u62a5\u544a: http://bugs.python.org/issue10544\n",
        "- \u8fd9\u4e2abug\u57283.7\u4ee5\u540e\u7684\u7248\u672c\u4e2d\u4e0d\u88ab\u63a8\u8350\u4f7f\u7528, \u5e76\u57283.8\u4e2d\u88ab\u4fee\u590d. \u56e0\u6b64\u57283.8\u4e2d\u5c1d\u8bd5\u5728\u63a8\u5bfc\u5f0f\u4e2d\u4f7f\u7528 yield, \u53ea\u4f1a\u5f97\u5230\u4e00\u4e2a SyntaxError. \u8be6\u7ec6\u5185\u5bb9\u53ef\u4ee5\u770b[3.7\u66f4\u65b0\u5185\u5bb9](https://docs.python.org/dev/whatsnew/3.7.html#deprecated-python-behavior), [3.8\u66f4\u65b0\u5185\u5bb9](https://docs.python.org/dev/whatsnew/3.8.html#changes-in-python-behavior).\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Yielding from... return!/\u751f\u6210\u5668\u91cc\u7684return *\n",
        "1\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_func(x):\n",
        "    if x == 3:\n",
        "        return [\"wtf\"]\n",
        "    else:\n",
        "        yield from range(x)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (> 3.3):**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list(some_func(3))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "`\"wtf\"` \u53bb\u54ea\u513f\u4e86\uff1f\u662f\u56e0\u4e3a`yield from`\u7684\u4e00\u4e9b\u7279\u6b8a\u6548\u679c\u5417\uff1f\u8ba9\u6211\u4eec\u9a8c\u8bc1\u4e00\u4e0b\n",
        "\n",
        "2\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_func(x):\n",
        "    if x == 3:\n",
        "        return [\"wtf\"]\n",
        "    else:\n",
        "        for i in range(x):\n",
        "          yield i\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list(some_func(3))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u540c\u6837\u7684\u7ed3\u679c\uff0c\u8fd9\u91cc\u4e5f\u4e0d\u8d77\u4f5c\u7528\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "+ \u4ece Python 3.3 \u5f00\u59cb\uff0c\u53ef\u4ee5\u5728\u751f\u6210\u5668\u4e2d\u4f7f\u7528\u5e26\u6709\u503c\u7684 `return` \u8bed\u53e5\uff08\u53c2\u89c1 [PEP380](https://www.python.org/dev/peps/pep-0380/)\uff09\u3002 [\u5b98\u65b9\u6587\u6863](https://www.python.org/dev/peps/pep-0380/#enhancements-to-stopiteration) \u63cf\u8ff0\uff0c\n",
        "\n",
        "> \"... \u751f\u6210\u5668\u4e2d\u7684 `return expr` \u4f1a\u5bfc\u81f4\u5728\u9000\u51fa\u751f\u6210\u5668\u65f6\u5f15\u53d1 `StopIteration(expr)`\u3002\"\n",
        "\n",
        "+ \u5728 `some_func(3)` \u4f8b\u5b50\u4e2d\uff0c`return` \u8bed\u53e5\u5728\u5f00\u59cb\u5c31\u5f15\u53d1\u4e86`StopIteration`\u3002 `StopIteration` \u5f02\u5e38\u4f1a\u5728`list(...)` \u5305\u88c5\u5668\u548c`for` \u5faa\u73af\u4e2d\u81ea\u52a8\u6355\u83b7\u3002 \u56e0\u6b64\uff0c\u4ee5\u4e0a\u4e24\u4e2a\u7247\u6bb5\u90fd\u4ea7\u751f\u7684\u662f\u4e00\u4e2a\u7a7a\u5217\u8868\u3002\n",
        "\n",
        "+ \u8981\u4ece\u751f\u6210\u5668 `some_func` \u4e2d\u83b7\u53d6 `[\"wtf\"]`\uff0c\u6211\u4eec\u9700\u8981\u6355\u83b7 `StopIteration` \u5f02\u5e38\uff0c\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    try:\n",
        "        next(some_func(3))\n",
        "    except StopIteration as e:\n",
        "        some_string = e.value\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    [\"wtf\"]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_string\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Nan-reflexivity/Nan\u7684\u81ea\u53cd\u6027\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = float('inf')\n",
        "b = float('nan')\n",
        "c = float('-iNf')  # \u8fd9\u4e9b\u5b57\u7b26\u4e32\u4e0d\u533a\u5206\u5927\u5c0f\u5199\n",
        "d = float('nan')\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "inf\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "nan\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "-inf\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "ValueError: could not convert string to float: some_other_string\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "float('some_other_string')\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a == -c #inf==inf\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "None == None # None==None\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "b == d #\u4f46\u662f nan!=nan\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0.0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "50/a\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "nan\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a/a\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "nan\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "23 + b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = float('nan')\n",
        "y = x / x\n",
        "y is y # \u540c\u4e00\u6027(identity)\u5177\u5907\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "y == y # y\u4e0d\u5177\u5907\u76f8\u7b49\u6027(equality)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "[y] == [y] # \u4f46\u5305\u542by\u7684\u5217\u8868\u9a8c\u8bc1\u76f8\u7b49\u6027(equality)\u6210\u529f\u4e86\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "`'inf'` \u548c `'nan'` \u662f\u7279\u6b8a\u7684\u5b57\u7b26\u4e32(\u4e0d\u533a\u5206\u5927\u5c0f\u5199), \u5f53\u663e\u793a\u8f6c\u6362\u6210 `float` \u578b\u65f6, \u5b83\u4eec\u5206\u522b\u7528\u4e8e\u8868\u793a\u6570\u5b66\u610f\u4e49\u4e0a\u7684 \"\u65e0\u7a77\u5927\" \u548c \"\u975e\u6570\u5b57\".\n",
        "- \u7531\u4e8e\u6839\u636e IEEE \u6807\u51c6 `NaN != NaN`\uff0c\u9075\u5b88\u6b64\u89c4\u5219\u6253\u7834\u4e86 Python \u4e2d\u96c6\u5408\u5143\u7d20\u7684\u81ea\u53cd\u6027\u5047\u8bbe\uff0c\u5373\u5982\u679c `x` \u662f `list` \u7b49\u96c6\u5408\u7684\u4e00\u90e8\u5206\uff0c\u5219\u6bd4\u8f83\u7b49\u8fd0\u7b97\u7684\u5b9e\u73b0\u57fa\u4e8e\u5047\u8bbe`x == x`\u3002\u7531\u4e8e\u8fd9\u4e2a\u5047\u8bbe\uff0c\u5728\u6bd4\u8f83\u4e24\u4e2a\u5143\u7d20\u65f6\u9996\u5148\u6bd4\u8f83\u8eab\u4efd`identity`\uff08\u56e0\u4e3a\u5b83\u66f4\u5feb\uff09\uff0c\u5e76\u4e14\u4ec5\u5728\u8eab\u4efd\u4e0d\u5339\u914d\u65f6\u624d\u6bd4\u8f83\u503c\u3002\u4ee5\u4e0b\u7247\u6bb5\u5c06\u66f4\u6e05\u695a\u5730\u8bf4\u660e\uff0c\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  (False, True)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  x = float('nan')\n",
        "  x == x, [x] == [x]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  (False, True)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  y = float('nan')\n",
        "  y == y, [y] == [y]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  (False, False)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  x == y, [x] == [y]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  \u7531\u4e8e `x` \u548c `y` \u7684\u8eab\u4efd`identity`\u4e0d\u540c\uff0c\u6240\u4ee5\u8003\u8651\u7684\u503c\u4e5f\u4e0d\u540c\uff1b \u56e0\u6b64\u8fd9\u6b21\u6bd4\u8f83\u8fd4\u56de\u201cFalse\u201d\u3002\n",
        "\n",
        "\n",
        "- \u611f\u5174\u8da3\u53ef\u4ee5\u9605\u8bfb [Reflexivity, and other pillars of civilization](https://bertrandmeyer.com/2010/02/06/reflexivity-and-other-pillars-of-civilization/)\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Mutating the immutable!/\u5f3a\u4eba\u6240\u96be\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_tuple = (\"A\", \"tuple\", \"with\", \"values\")\n",
        "another_tuple = ([1, 2], [3, 4], [5, 6])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "TypeError: 'tuple' object does not support item assignment\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_tuple[2] = \"change this\"\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "([1, 2], [3, 4], [5, 6, 1000])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_tuple[2].append(1000) # \u8fd9\u91cc\u4e0d\u51fa\u73b0\u9519\u8bef\n",
        "another_tuple\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "TypeError: 'tuple' object does not support item assignment\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_tuple[2] += [99, 999]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "([1, 2], [3, 4], [5, 6, 1000, 99, 999])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_tuple\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u6211\u8fd8\u4ee5\u4e3a\u5143\u7ec4\u662f\u4e0d\u53ef\u53d8\u7684\u5462...\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5f15\u7528 https://docs.python.org/2/reference/datamodel.html\n",
        "\n",
        "    > \u4e0d\u53ef\u53d8\u5e8f\u5217\n",
        "        \u4e0d\u53ef\u53d8\u5e8f\u5217\u7684\u5bf9\u8c61\u4e00\u65e6\u521b\u5efa\u5c31\u4e0d\u80fd\u518d\u6539\u53d8. (\u5982\u679c\u5bf9\u8c61\u5305\u542b\u5bf9\u5176\u4ed6\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u5219\u8fd9\u4e9b\u5176\u4ed6\u5bf9\u8c61\u53ef\u80fd\u662f\u53ef\u53d8\u7684\u5e76\u4e14\u53ef\u80fd\u4f1a\u88ab\u4fee\u6539; \u4f46\u662f\uff0c\u7531\u4e0d\u53ef\u53d8\u5bf9\u8c61\u76f4\u63a5\u5f15\u7528\u7684\u5bf9\u8c61\u96c6\u5408\u4e0d\u80fd\u66f4\u6539.)\n",
        "\n",
        "* `+=` \u64cd\u4f5c\u7b26\u5728\u539f\u5730\u4fee\u6539\u4e86\u5217\u8868. \u5143\u7d20\u8d4b\u503c\u64cd\u4f5c\u5e76\u4e0d\u5de5\u4f5c, \u4f46\u662f\u5f53\u5f02\u5e38\u629b\u51fa\u65f6, \u5143\u7d20\u5df2\u7ecf\u5728\u539f\u5730\u88ab\u4fee\u6539\u4e86.\n",
        "\n",
        "(\u8bd1: \u5bf9\u4e8e\u4e0d\u53ef\u53d8\u5bf9\u8c61, \u8fd9\u91cc\u6307tuple, `+=` \u5e76\u4e0d\u662f\u539f\u5b50\u64cd\u4f5c, \u800c\u662f `extend` \u548c `=` \u4e24\u4e2a\u52a8\u4f5c, \u8fd9\u91cc `=` \u64cd\u4f5c\u867d\u7136\u4f1a\u629b\u51fa\u5f02\u5e38, \u4f46 `extend` \u64cd\u4f5c\u5df2\u7ecf\u4fee\u6539\u6210\u529f\u4e86. \u8be6\u7ec6\u89e3\u91ca\u53ef\u4ee5\u770b[\u8fd9\u91cc](https://segmentfault.com/a/1190000010767068))\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > The disappearing variable from outer scope/\u6d88\u5931\u7684\u5916\u90e8\u53d8\u91cf\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "e = 7\n",
        "try:\n",
        "    raise Exception()\n",
        "except Exception as e:\n",
        "    pass\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "# prints nothing\n"
          ]
        }
      ],
      "source": [
        "print(e)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "NameError: name 'e' is not defined\n"
          ]
        }
      ],
      "source": [
        "print(e)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u51fa\u5904: https://docs.python.org/3/reference/compound_stmts.html#except\n",
        "\n",
        "  \u5f53\u4f7f\u7528 `as` \u4e3a\u76ee\u6807\u5206\u914d\u5f02\u5e38\u7684\u65f6\u5019, \u5c06\u5728except\u5b50\u53e5\u7684\u672b\u5c3e\u6e05\u9664\u8be5\u5f02\u5e38.\n",
        "\n",
        "  \u8fd9\u5c31\u597d\u50cf\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  except E as N:\n",
        "      foo\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  \u4f1a\u88ab\u7ffb\u8bd1\u6210\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  except E as N:\n",
        "      try:\n",
        "          foo\n",
        "      finally:\n",
        "          del N\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  \u8fd9\u610f\u5473\u7740\u5f02\u5e38\u5fc5\u987b\u5728\u88ab\u8d4b\u503c\u7ed9\u5176\u4ed6\u53d8\u91cf\u624d\u80fd\u5728 `except` \u5b50\u53e5\u4e4b\u540e\u5f15\u7528\u5b83. \u800c\u5f02\u5e38\u4e4b\u6240\u4ee5\u4f1a\u88ab\u6e05\u9664, \u5219\u662f\u7531\u4e8e\u4e0a\u9762\u9644\u52a0\u7684\u56de\u6eaf\u4fe1\u606f(trackback)\u4f1a\u548c\u6808\u5e27(stack frame)\u5f62\u6210\u5faa\u73af\u5f15\u7528, \u4f7f\u5f97\u8be5\u6808\u5e27\u4e2d\u7684\u6240\u6709\u672c\u5730\u53d8\u91cf\u5728\u4e0b\u4e00\u6b21\u5783\u573e\u56de\u6536\u53d1\u751f\u4e4b\u524d\u90fd\u5904\u4e8e\u6d3b\u52a8\u72b6\u6001.(\u8bd1: \u4e5f\u5c31\u662f\u8bf4\u4e0d\u4f1a\u88ab\u56de\u6536)\n",
        "\n",
        "* \u5b50\u53e5\u5728 Python \u4e2d\u5e76\u6ca1\u6709\u72ec\u7acb\u7684\u4f5c\u7528\u57df. \u793a\u4f8b\u4e2d\u7684\u6240\u6709\u5185\u5bb9\u90fd\u5904\u4e8e\u540c\u4e00\u4f5c\u7528\u57df\u5185, \u6240\u4ee5\u53d8\u91cf `e` \u4f1a\u7531\u4e8e\u6267\u884c\u4e86 `except` \u5b50\u53e5\u800c\u88ab\u5220\u9664. \u800c\u5bf9\u4e8e\u6709\u72ec\u7acb\u7684\u5185\u90e8\u4f5c\u7528\u57df\u7684\u51fd\u6570\u6765\u8bf4\u60c5\u51b5\u5c31\u4e0d\u4e00\u6837\u4e86. \u4e0b\u9762\u7684\u4f8b\u5b50\u8bf4\u660e\u4e86\u8fd9\u4e00\u70b9:\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "     def f(x):\n",
        "         del(x)\n",
        "         print(x)\n",
        "\n",
        "     x = 5\n",
        "     y = [5, 4, 3]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "     **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "     5\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "     >>>f(x)\n",
        "     UnboundLocalError: local variable 'x' referenced before assignment\n",
        "     >>>f(y)\n",
        "     UnboundLocalError: local variable 'x' referenced before assignment\n",
        "     x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "     [5, 4, 3]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "     y\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5728 Python 2.x \u4e2d, `Exception()` \u5b9e\u4f8b\u88ab\u8d4b\u503c\u7ed9\u4e86\u53d8\u91cf `e`, \u6240\u4ee5\u5f53\u4f60\u5c1d\u8bd5\u6253\u5370\u7ed3\u679c\u7684\u65f6\u5019, \u5b83\u7684\u8f93\u51fa\u4e3a\u7a7a.\uff08\u8bd1: \u6b63\u5e38\u7684Exception\u5b9e\u4f8b\u6253\u5370\u51fa\u6765\u5c31\u662f\u7a7a\uff09\n",
        "\n",
        "    **Output (Python 2.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    Exception()\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    e\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    # \u6ca1\u6709\u6253\u5370\u4efb\u4f55\u5185\u5bb9!\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    print e\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > The mysterious key type conversion/\u795e\u79d8\u7684\u952e\u578b\u8f6c\u6362 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class SomeClass(str):\n",
        "    pass\n",
        "\n",
        "some_dict = {'s':42}\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "str\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "type(list(some_dict.keys())[0])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "{'s': 40}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "s = SomeClass('s')\n",
        "some_dict[s] = 40\n",
        "some_dict # \u9884\u671f: \u4e24\u4e2a\u4e0d\u540c\u7684\u952e\u503c\u5bf9\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "str\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "type(list(some_dict.keys())[0])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u7531\u4e8e `SomeClass` \u4f1a\u4ece `str` \u81ea\u52a8\u7ee7\u627f `__hash__` \u65b9\u6cd5, \u6240\u4ee5 `s` \u5bf9\u8c61\u548c `\"s\"` \u5b57\u7b26\u4e32\u7684\u54c8\u5e0c\u503c\u662f\u76f8\u540c\u7684.\n",
        "* \u800c `SomeClass(\"s\") == \"s\"` \u4e3a `True` \u662f\u56e0\u4e3a `SomeClass` \u4e5f\u7ee7\u627f\u4e86 `str` \u7c7b `__eq__` \u65b9\u6cd5.\n",
        "* \u7531\u4e8e\u4e24\u8005\u7684\u54c8\u5e0c\u503c\u76f8\u540c\u4e14\u76f8\u7b49, \u6240\u4ee5\u5b83\u4eec\u5728\u5b57\u5178\u4e2d\u8868\u793a\u76f8\u540c\u7684\u952e.\n",
        "* \u5982\u679c\u60f3\u8981\u5b9e\u73b0\u671f\u671b\u7684\u529f\u80fd, \u6211\u4eec\u53ef\u4ee5\u91cd\u5b9a\u4e49 `SomeClass` \u7684 `__eq__` \u65b9\u6cd5.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  class SomeClass(str):\n",
        "    def __eq__(self, other):\n",
        "        return (\n",
        "            type(self) is SomeClass\n",
        "            and type(other) is SomeClass\n",
        "            and super().__eq__(other)\n",
        "        )\n",
        "\n",
        "    # \u5f53\u6211\u4eec\u81ea\u5b9a\u4e49 __eq__ \u65b9\u6cd5\u65f6, Python \u4e0d\u4f1a\u518d\u81ea\u52a8\u7ee7\u627f __hash__ \u65b9\u6cd5\n",
        "    # \u6240\u4ee5\u6211\u4eec\u4e5f\u9700\u8981\u5b9a\u4e49\u5b83\n",
        "    __hash__ = str.__hash__\n",
        "\n",
        "  some_dict = {'s':42}\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  {'s': 40, 's': 42}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  s = SomeClass('s')\n",
        "  some_dict[s] = 40\n",
        "  some_dict\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  (__main__.SomeClass, str)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  keys = list(some_dict.keys())\n",
        "  type(keys[0]), type(keys[1])\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Let's see if you can guess this?/\u770b\u770b\u4f60\u80fd\u5426\u731c\u5230\u8fd9\u4e00\u70b9?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a, b = a[b] = {}, 5\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "{5: ({...}, 5)}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u6839\u636e [Python \u8bed\u8a00\u53c2\u8003](https://docs.python.org/2/reference/simple_stmts.html#assignment-statements), \u8d4b\u503c\u8bed\u53e5\u7684\u5f62\u5f0f\u5982\u4e0b\n",
        "  ```\n",
        "  (target_list \"=\")+ (expression_list | yield_expression)\n",
        "  ```\n",
        "\n",
        "  > \u8d4b\u503c\u8bed\u53e5\u8ba1\u7b97\u8868\u8fbe\u5f0f\u5217\u8868(expression list)(\u7262\u8bb0 \u8fd9\u53ef\u4ee5\u662f\u5355\u4e2a\u8868\u8fbe\u5f0f\u6216\u4ee5\u9017\u53f7\u5206\u9694\u7684\u5217\u8868, \u540e\u8005\u8fd4\u56de\u5143\u7ec4)\u5e76\u5c06\u5355\u4e2a\u7ed3\u679c\u5bf9\u8c61\u4ece\u5de6\u5230\u53f3\u5206\u914d\u7ed9\u76ee\u6807\u5217\u8868\u4e2d\u7684\u6bcf\u4e00\u9879.\n",
        "\n",
        "*  `(target_list \"=\")+` \u4e2d\u7684 `+` \u610f\u5473\u7740\u53ef\u4ee5\u6709**\u4e00\u4e2a\u6216\u591a\u4e2a**\u76ee\u6807\u5217\u8868. \u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d, \u76ee\u6807\u5217\u8868\u662f `a, b` \u548c `a[b]` (\u6ce8\u610f\u8868\u8fbe\u5f0f\u5217\u8868\u53ea\u80fd\u6709\u4e00\u4e2a, \u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d\u662f `{}, 5`).\n",
        "\n",
        "* \u8868\u8fbe\u5f0f\u5217\u8868\u8ba1\u7b97\u7ed3\u675f\u540e, \u5c06\u5176\u503c\u81ea\u52a8\u89e3\u5305\u540e**\u4ece\u5de6\u5230\u53f3**\u5206\u914d\u7ed9\u76ee\u6807\u5217\u8868(target list). \u56e0\u6b64, \u5728\u6211\u4eec\u7684\u4f8b\u5b50\u4e2d, \u9996\u5148\u5c06 `{}, 5` \u5143\u7ec4\u5e76\u8d4b\u503c\u7ed9 `a, b`, \u7136\u540e\u6211\u4eec\u5c31\u53ef\u4ee5\u5f97\u5230 `a = {}` \u4e14 `b = 5`.\n",
        "\n",
        "* `a` \u88ab\u8d4b\u503c\u7684 `{}` \u662f\u53ef\u53d8\u5bf9\u8c61.\n",
        "\n",
        "* \u7b2c\u4e8c\u4e2a\u76ee\u6807\u5217\u8868\u662f `a[b]` (\u4f60\u53ef\u80fd\u89c9\u5f97\u8fd9\u91cc\u4f1a\u62a5\u9519, \u56e0\u4e3a\u5728\u4e4b\u524d\u7684\u8bed\u53e5\u4e2d `a` \u548c `b` \u90fd\u8fd8\u6ca1\u6709\u88ab\u5b9a\u4e49. \u4f46\u662f\u522b\u5fd8\u4e86, \u6211\u4eec\u521a\u521a\u5c06 `a` \u8d4b\u503c `{}` \u4e14\u5c06 `b` \u8d4b\u503c\u4e3a `5`).\n",
        "\n",
        "* \u73b0\u5728, \u6211\u4eec\u5c06\u901a\u8fc7\u5c06\u5b57\u5178\u4e2d\u952e `5` \u7684\u503c\u8bbe\u7f6e\u4e3a\u5143\u7ec4 `({}, 5)` \u6765\u521b\u5efa\u5faa\u73af\u5f15\u7528 (\u8f93\u51fa\u4e2d\u7684 `{...}` \u6307\u4e0e `a` \u5f15\u7528\u4e86\u76f8\u540c\u7684\u5bf9\u8c61). \u4e0b\u9762\u662f\u4e00\u4e2a\u66f4\u7b80\u5355\u7684\u5faa\u73af\u5f15\u7528\u7684\u4f8b\u5b50\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  [[...]]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list = some_list[0] = [0]\n",
        "  some_list\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  [[...]]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list[0]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list is some_list[0]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list[0][0][0][0][0][0] == some_list\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  \u6211\u4eec\u7684\u4f8b\u5b50\u5c31\u662f\u8fd9\u79cd\u60c5\u51b5 (`a[b][0]` \u4e0e `a` \u662f\u76f8\u540c\u7684\u5bf9\u8c61)\n",
        "\n",
        "* \u603b\u7ed3\u4e00\u4e0b, \u4f60\u4e5f\u53ef\u4ee5\u628a\u4f8b\u5b50\u62c6\u6210\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  a, b = {}, 5\n",
        "  a[b] = a, b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  \u5e76\u4e14\u53ef\u4ee5\u901a\u8fc7 `a[b][0]` \u4e0e `a` \u662f\u76f8\u540c\u7684\u5bf9\u8c61\u6765\u8bc1\u660e\u662f\u5faa\u73af\u5f15\u7528\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  a[b][0] is a\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Exceeds the limit for integer string conversion/\u6574\u578b\u8f6c\u5b57\u7b26\u4e32\u8d8a\u754c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# Python 3.10.6\n",
        "int(\"2\" * 5432)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# Python 3.10.8\n",
        "int(\"2\" * 5432)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "222222222222222222222222222222222222222222222222222222222222222...\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# Python 3.10.6\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# Python 3.10.8\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "ValueError: Exceeds the limit (4300) for integer string conversion:\n",
              "   value has 5432 digits; use sys.set_int_max_str_digits()\n",
              "   to increase the limit.\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "   \n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5bf9`int()`\u7684\u8c03\u7528\u5728Python 3.10.6\u4e2d\u8fd0\u884c\u826f\u597d\uff0c\u4f46\u5728Python 3.10.8\u4e2d\u5f15\u53d1ValueError\u3002\u8bf7\u6ce8\u610f\uff0cPython\u4ecd\u7136\u53ef\u4ee5\u5904\u7406\u5927\u6574\u6570\u3002\u53ea\u6709\u5728\u6574\u578b\u548c\u5b57\u7b26\u4e32\u4e4b\u95f4\u8f6c\u6362\u65f6\u624d\u4f1a\u51fa\u73b0\u6b64\u9519\u8bef\u3002\n",
        "* \u5e78\u8fd0\u7684\u662f\uff0c\u5f53\u60a8\u5e0c\u671b\u64cd\u4f5c\u8d85\u8fc7\u5141\u8bb8\u7684\u4f4d\u6570\u9650\u5236\u65f6\uff0c\u53ef\u4ee5\u589e\u52a0\u8be5\u9650\u5236\u7684\u4e0a\u9650\u3002\u4e3a\u6b64\uff0c\u53ef\u4ee5\u4f7f\u7528\u4ee5\u4e0b\u65b9\u6cd5\u4e4b\u4e00\uff1a\n",
        "    - \u4f7f\u7528 -X int_max_str_digits \u7684\u547d\u4ee4\u884c\u53c2\u6570\uff08\u4f8b\u5982\uff0c python3 -X int_max_str_digits=640\uff09\n",
        "    - \u4f7f\u7528\u6765\u81easys\u6a21\u5757\u7684set_int_max_str_digits()\u51fd\u6570\n",
        "    - \u8bbe\u5b9a PYTHONINTMAXSTRDIGITS \u73af\u5883\u53d8\u91cf\n",
        "\n",
        "\u66f4\u591a\u66f4\u6539\u8bbe\u7f6e\u4e0a\u9650\u7684\u64cd\u4f5c\u7ec6\u8282\u67e5\u770b[\u6587\u6863](https://docs.python.org/3/library/stdtypes.html#int-max-str-digits)\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Modifying a dictionary while iterating over it/\u8fed\u4ee3\u5b57\u5178\u65f6\u7684\u4fee\u6539\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = {0: None}\n",
        "\n",
        "for i in x:\n",
        "    del x[i]\n",
        "    x[i+1] = None\n",
        "    print(i)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.7- Python 3.5):**\n",
        "\n",
        "```\n",
        "0\n",
        "1\n",
        "2\n",
        "3\n",
        "4\n",
        "5\n",
        "6\n",
        "7\n",
        "```\n",
        "\n",
        "\u662f\u7684, \u5b83\u8fd0\u884c\u4e86**\u516b\u6b21**\u7136\u540e\u624d\u505c\u4e0b\u6765.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* Python\u4e0d\u652f\u6301\u5bf9\u5b57\u5178\u8fdb\u884c\u8fed\u4ee3\u7684\u540c\u65f6\u4fee\u6539\u5b83.\n",
        "* \u5b83\u4e4b\u6240\u4ee5\u8fd0\u884c8\u6b21, \u662f\u56e0\u4e3a\u5b57\u5178\u4f1a\u81ea\u52a8\u6269\u5bb9\u4ee5\u5bb9\u7eb3\u66f4\u591a\u952e\u503c(\u6211\u4eec\u67098\u6b21\u5220\u9664\u8bb0\u5f55, \u56e0\u6b64\u9700\u8981\u6269\u5bb9). \u8fd9\u5b9e\u9645\u4e0a\u662f\u4e00\u4e2a\u5b9e\u73b0\u7ec6\u8282. (\u8bd1: \u5e94\u8be5\u662f\u56e0\u4e3a\u5b57\u5178\u7684\u521d\u59cb\u6700\u5c0f\u503c\u662f8, \u6269\u5bb9\u4f1a\u5bfc\u81f4\u6563\u5217\u8868\u5730\u5740\u53d1\u751f\u53d8\u5316\u800c\u4e2d\u65ad\u5faa\u73af.)\n",
        "* \u5728\u4e0d\u540c\u7684Python\u5b9e\u73b0\u4e2d\u5220\u9664\u952e\u7684\u5904\u7406\u65b9\u5f0f\u4ee5\u53ca\u8c03\u6574\u5927\u5c0f\u7684\u65f6\u95f4\u53ef\u80fd\u4f1a\u6709\u6240\u4e0d\u540c.(\u8bd1: \u5c31\u662f\u8bf4\u4ec0\u4e48\u65f6\u5019\u6269\u5bb9\u5728\u4e0d\u540c\u7248\u672c\u4e2d\u53ef\u80fd\u662f\u4e0d\u540c\u7684, \u57283.6\u53ca3.7\u7684\u7248\u672c\u4e2d\u5230[5](https://github.com/python/cpython/blob/v3.6.1/Objects/dictobject.c#L103-L110)\u5c31\u4f1a\u81ea\u52a8\u6269\u5bb9\u4e86. \u4ee5\u540e\u4e5f\u6709\u53ef\u80fd\u518d\u6b21\u53d1\u751f\u53d8\u5316. \u8fd9\u662f\u4e3a\u4e86\u907f\u514d\u6563\u5217\u51b2\u7a81. \u987a\u5e26\u4e00\u63d0, \u540e\u9762\u4e24\u6b21\u6269\u5bb9\u4f1a\u6269\u5c55\u4e3a32\u548c256. \u5373`8->32->256`.)\n",
        "* \u66f4\u591a\u7684\u4fe1\u606f, \u4f60\u53ef\u4ee5\u53c2\u8003\u8fd9\u4e2aStackOverflow\u7684[\u56de\u7b54](https://stackoverflow.com/questions/44763802/bug-in-python-dict), \u5b83\u8be6\u7ec6\u7684\u89e3\u91ca\u4e00\u4e2a\u7c7b\u4f3c\u7684\u4f8b\u5b50.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Stubborn `del` operator/\u575a\u5f3a\u7684 `del` *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class SomeClass:\n",
        "    def __del__(self):\n",
        "        print(\"Deleted!\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Deleted!\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = SomeClass()\n",
        "y = x\n",
        "del x # \u8fd9\u91cc\u5e94\u8be5\u4f1a\u8f93\u51fa \"Deleted!\"\n",
        "del y\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5537, \u7ec8\u4e8e\u5220\u9664\u4e86. \u4f60\u53ef\u80fd\u5df2\u7ecf\u731c\u5230\u4e86\u5728\u6211\u4eec\u7b2c\u4e00\u6b21\u5c1d\u8bd5\u5220\u9664 `x` \u65f6\u662f\u4ec0\u4e48\u8ba9 `__del__` \u514d\u4e8e\u88ab\u8c03\u7528\u7684. \u90a3\u8ba9\u6211\u4eec\u7ed9\u8fd9\u4e2a\u4f8b\u5b50\u589e\u52a0\u70b9\u96be\u5ea6.\n",
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<__main__.SomeClass instance at 0x7f98a1a67fc8>\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = SomeClass()\n",
        "y = x\n",
        "del x\n",
        "y # \u68c0\u67e5\u4e00\u4e0by\u662f\u5426\u5b58\u5728\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Deleted!\n",
              "{'__builtins__': <module '__builtin__' (built-in)>, 'SomeClass': <class __main__.SomeClass at 0x7f98a1a5f668>, '__package__': None, '__name__': '__main__', '__doc__': None}\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "del y # \u50cf\u4e4b\u524d\u4e00\u6837, \u8fd9\u91cc\u5e94\u8be5\u4f1a\u8f93\u51fa \"Deleted!\"\n",
        "globals() # \u597d\u5427, \u5e76\u6ca1\u6709. \u8ba9\u6211\u4eec\u770b\u4e00\u4e0b\u6240\u6709\u7684\u5168\u5c40\u53d8\u91cf\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u597d\u4e86\uff0c\u73b0\u5728\u5b83\u88ab\u5220\u9664\u4e86 :confused:\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "+ `del x` \u5e76\u4e0d\u4f1a\u7acb\u523b\u8c03\u7528 `x.__del__()`.\n",
        "+ \u6bcf\u5f53\u9047\u5230 `del x`, Python \u4f1a\u5c06 `x` \u7684\u5f15\u7528\u6570\u51cf1, \u5f53 `x` \u7684\u5f15\u7528\u6570\u51cf\u52300\u65f6\u5c31\u4f1a\u8c03\u7528 `x.__del__()`.\n",
        "+ \u5728\u7b2c\u4e8c\u4e2a\u4f8b\u5b50\u4e2d, `y.__del__()` \u4e4b\u6240\u4ee5\u672a\u88ab\u8c03\u7528, \u662f\u56e0\u4e3a\u524d\u4e00\u6761\u8bed\u53e5 (`>>> y`) \u5bf9\u540c\u4e00\u5bf9\u8c61\u521b\u5efa\u4e86\u53e6\u4e00\u4e2a\u5f15\u7528, \u4ece\u800c\u9632\u6b62\u5728\u6267\u884c `del y` \u540e\u5bf9\u8c61\u7684\u5f15\u7528\u6570\u53d8\u4e3a0.\n",
        "+ \u8c03\u7528 `globals` \u5bfc\u81f4\u5f15\u7528\u88ab\u9500\u6bc1, \u56e0\u6b64\u6211\u4eec\u53ef\u4ee5\u770b\u5230 \"Deleted!\" \u7ec8\u4e8e\u88ab\u8f93\u51fa\u4e86.\n",
        "+ (\u8bd1: \u8fd9\u5176\u5b9e\u662f Python \u4ea4\u4e92\u89e3\u91ca\u5668\u7684\u7279\u6027, \u5b83\u4f1a\u81ea\u52a8\u8ba9 `_` \u4fdd\u5b58\u4e0a\u4e00\u4e2a\u8868\u8fbe\u5f0f\u8f93\u51fa\u7684\u503c, \u8be6\u7ec6\u53ef\u4ee5\u770b[\u8fd9\u91cc](https://www.cnblogs.com/leisurelylicht/p/diao-pi-de-kong-zhi-tai.html).)\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > The out of scope variable/\u5916\u90e8\u4f5c\u7528\u57df\u53d8\u91cf\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = 1\n",
        "def some_func():\n",
        "    return a\n",
        "\n",
        "def another_func():\n",
        "    a += 1\n",
        "    return a\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_closure_func():\n",
        "    a = 1\n",
        "    def some_inner_func():\n",
        "        return a\n",
        "    return some_inner_func()\n",
        "\n",
        "def another_closure_func():\n",
        "    a = 1\n",
        "    def another_inner_func():\n",
        "        a += 1\n",
        "        return a\n",
        "    return another_inner_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "UnboundLocalError: local variable 'a' referenced before assignment\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_closure_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "UnboundLocalError: local variable 'a' referenced before assignment\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_closure_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "* \u5f53\u4f60\u5728\u4f5c\u7528\u57df\u4e2d\u5bf9\u53d8\u91cf\u8fdb\u884c\u8d4b\u503c\u65f6, \u53d8\u91cf\u4f1a\u53d8\u6210\u8be5\u4f5c\u7528\u57df\u5185\u7684\u5c40\u90e8\u53d8\u91cf. \u56e0\u6b64 `a` \u4f1a\u53d8\u6210 `another_func` \u51fd\u6570\u4f5c\u7528\u57df\u4e2d\u7684\u5c40\u90e8\u53d8\u91cf, \u4f46\u5b83\u5728\u51fd\u6570\u4f5c\u7528\u57df\u4e2d\u5e76\u6ca1\u6709\u88ab\u521d\u59cb\u5316, \u6240\u4ee5\u4f1a\u5f15\u53d1\u9519\u8bef.\n",
        "* \u60f3\u8981\u5728 `another_func` \u4e2d\u4fee\u6539\u5916\u90e8\u4f5c\u7528\u57df\u53d8\u91cf `a` \u7684\u8bdd, \u53ef\u4ee5\u4f7f\u7528 `global` \u5173\u952e\u5b57.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  def another_func()\n",
        "      global a\n",
        "      a += 1\n",
        "      return a\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  another_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5728 `another_closure_func` \u51fd\u6570\u4e2d\uff0c`a` \u4f1a\u53d8\u6210 `another_inner_func` \u51fd\u6570\u4f5c\u7528\u57df\u4e2d\u7684\u5c40\u90e8\u53d8\u91cf, \u4f46\u5b83\u5728\u540c\u4e00\u4f5c\u7528\u57df\u4e2d\u5e76\u6ca1\u6709\u88ab\u521d\u59cb\u5316, \u6240\u4ee5\u4f1a\u5f15\u53d1\u9519\u8bef\u3002\n",
        "* \u60f3\u8981\u5728 `another_inner_func` \u4e2d\u4fee\u6539\u5916\u90e8\u4f5c\u7528\u57df\u53d8\u91cf `a` \u7684\u8bdd, \u53ef\u4ee5\u4f7f\u7528 `nonlocal` \u5173\u952e\u5b57\u3002nonlocal \u8868\u8fbe\u5f0f\u7528\u4e8e\uff08\u9664\u5168\u5c40\u4f5c\u7528\u57df\u5916\uff09\u6700\u8fd1\u4e00\u7ea7\u7684\u5916\u90e8\u4f5c\u7528\u57df\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  def another_func():\n",
        "      a = 1\n",
        "      def another_inner_func():\n",
        "          nonlocal a\n",
        "          a += 1\n",
        "          return a\n",
        "      return another_inner_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  another_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "*  `global` and `nonlocal` \u5173\u952e\u5b57\u544a\u8bc9 `Python` \u89e3\u91ca\u5668\uff0c\u4e0d\u8981\u58f0\u660e\u65b0\u53d8\u91cf\uff0c\u800c\u662f\u5728\u76f8\u5e94\u7684\u5916\u90e8\u4f5c\u7528\u57df\u4e2d\u67e5\u627e\u53d8\u91cf\u3002\n",
        "* \u53ef\u4ee5\u9605\u8bfb[\u8fd9\u4e2a](https://sebastianraschka.com/Articles/2014_python_scope_and_namespaces.html)\u7b80\u77ed\u5374\u5f88\u68d2\u7684\u6307\u5357, \u4e86\u89e3\u66f4\u591a\u5173\u4e8e Python \u4e2d\u547d\u540d\u7a7a\u95f4\u548c\u4f5c\u7528\u57df\u7684\u5de5\u4f5c\u539f\u7406\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Deleting a list item while iterating/\u8fed\u4ee3\u5217\u8868\u65f6\u5220\u9664\u5143\u7d20\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list_1 = [1, 2, 3, 4]\n",
        "list_2 = [1, 2, 3, 4]\n",
        "list_3 = [1, 2, 3, 4]\n",
        "list_4 = [1, 2, 3, 4]\n",
        "\n",
        "for idx, item in enumerate(list_1):\n",
        "    del item\n",
        "\n",
        "for idx, item in enumerate(list_2):\n",
        "    list_2.remove(item)\n",
        "\n",
        "for idx, item in enumerate(list_3[:]):\n",
        "    list_3.remove(item)\n",
        "\n",
        "for idx, item in enumerate(list_4):\n",
        "    list_4.pop(idx)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[1, 2, 3, 4]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list_1\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[2, 4]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list_2\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list_3\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[2, 4]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list_4\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4f60\u80fd\u731c\u5230\u4e3a\u4ec0\u4e48\u8f93\u51fa\u662f `[2, 4]` \u5417?\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5728\u8fed\u4ee3\u65f6\u4fee\u6539\u5bf9\u8c61\u662f\u4e00\u4e2a\u5f88\u611a\u8822\u7684\u4e3b\u610f. \u6b63\u786e\u7684\u505a\u6cd5\u662f\u8fed\u4ee3\u5bf9\u8c61\u7684\u526f\u672c, `list_3[:]` \u5c31\u662f\u8fd9\u4e48\u505a\u7684.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "     139798789457608\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "     some_list = [1, 2, 3, 4]\n",
        "     id(some_list)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "     139798779601192\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "     id(some_list[:]) # \u6ce8\u610fpython\u4e3a\u5207\u7247\u5217\u8868\u521b\u5efa\u4e86\u65b0\u5bf9\u8c61.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**`del`, `remove` \u548c `pop` \u7684\u4e0d\u540c:**\n",
        "* `del var_name` \u53ea\u662f\u4ece\u672c\u5730\u6216\u5168\u5c40\u547d\u540d\u7a7a\u95f4\u4e2d\u5220\u9664\u4e86 `var_name` (\u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48 `list_1` \u6ca1\u6709\u53d7\u5230\u5f71\u54cd).\n",
        "* `remove` \u4f1a\u5220\u9664\u7b2c\u4e00\u4e2a\u5339\u914d\u5230\u7684\u6307\u5b9a\u503c, \u800c\u4e0d\u662f\u7279\u5b9a\u7684\u7d22\u5f15, \u5982\u679c\u627e\u4e0d\u5230\u503c\u5219\u629b\u51fa `ValueError` \u5f02\u5e38.\n",
        "* `pop` \u5219\u4f1a\u5220\u9664\u6307\u5b9a\u7d22\u5f15\u5904\u7684\u5143\u7d20\u5e76\u8fd4\u56de\u5b83, \u5982\u679c\u6307\u5b9a\u4e86\u65e0\u6548\u7684\u7d22\u5f15\u5219\u629b\u51fa `IndexError` \u5f02\u5e38.\n",
        "\n",
        "**\u4e3a\u4ec0\u4e48\u8f93\u51fa\u662f `[2, 4]`?**\n",
        "- \u5217\u8868\u8fed\u4ee3\u662f\u6309\u7d22\u5f15\u8fdb\u884c\u7684, \u6240\u4ee5\u5f53\u6211\u4eec\u4ece `list_2` \u6216 `list_4` \u4e2d\u5220\u9664 `1` \u65f6, \u5217\u8868\u7684\u5185\u5bb9\u5c31\u53d8\u6210\u4e86 `[2, 3, 4]`. \u5269\u4f59\u5143\u7d20\u4f1a\u4f9d\u6b21\u4f4d\u79fb, \u4e5f\u5c31\u662f\u8bf4, `2` \u7684\u7d22\u5f15\u4f1a\u53d8\u4e3a 0, `3` \u4f1a\u53d8\u4e3a 1. \u7531\u4e8e\u4e0b\u4e00\u6b21\u8fed\u4ee3\u5c06\u83b7\u53d6\u7d22\u5f15\u4e3a 1 \u7684\u5143\u7d20 (\u5373 `3`), \u56e0\u6b64 `2` \u5c06\u88ab\u5f7b\u5e95\u7684\u8df3\u8fc7. \u7c7b\u4f3c\u7684\u60c5\u51b5\u4f1a\u4ea4\u66ff\u53d1\u751f\u5728\u5217\u8868\u4e2d\u7684\u6bcf\u4e2a\u5143\u7d20\u4e0a.\n",
        "\n",
        "* \u53c2\u8003\u8fd9\u4e2aStackOverflow\u7684[\u56de\u7b54](https://stackoverflow.com/questions/45946228/what-happens-when-you-try-to-delete-a-list-element-while-iterating-over-it)\u6765\u89e3\u91ca\u8fd9\u4e2a\u4f8b\u5b50\n",
        "* \u5173\u4e8ePython\u4e2d\u5b57\u5178\u7684\u7c7b\u4f3c\u4f8b\u5b50, \u53ef\u4ee5\u53c2\u8003\u8fd9\u4e2aStackoverflow\u7684[\u56de\u7b54](https://stackoverflow.com/questions/45877614/how-to-change-all-the-dictionary-keys-in-a-for-loop-with-d-items).\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Lossy zip of iterators/\u4e22\u4e09\u843d\u56db\u7684zip *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[0, 1, 2, 3, 4, 5, 6]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "numbers = list(range(7))\n",
        "numbers\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "([0, 1, 2], [3, 4, 5, 6])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "first_three, remaining = numbers[:3], numbers[3:]\n",
        "first_three, remaining\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[(0, 0), (1, 1), (2, 2)]\n",
              "# so far so good, let's zip the remaining\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "numbers_iter = iter(numbers)\n",
        "list(zip(numbers_iter, first_three)) \n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[(4, 3), (5, 4), (6, 5)]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list(zip(numbers_iter, remaining))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "`numbers` \u5217\u8868\u4e2d\u7684\u5143\u7d20 `3` \u54ea\u91cc\u53bb\u4e86\uff1f\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- \u6839\u636ePython [\u6587\u6863](https://docs.python.org/3.3/library/functions.html#zip)\uff0c `zip` \u51fd\u6570\u7684\u5927\u6982\u5b9e\u73b0\u5982\u4e0b\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    def zip(*iterables):\n",
        "        sentinel = object()\n",
        "        iterators = [iter(it) for it in iterables]\n",
        "        while iterators:\n",
        "            result = []\n",
        "            for it in iterators:\n",
        "                elem = next(it, sentinel)\n",
        "                if elem is sentinel: return\n",
        "                result.append(elem)\n",
        "            yield tuple(result)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u8be5\u51fd\u6570\u63a5\u53d7\u4efb\u610f\u6570\u91cf\u7684\u53ef\u8fed\u4ee3\u5bf9\u8c61\uff0c\u901a\u8fc7\u8c03\u7528 `next` \u51fd\u6570\u5c06\u5b83\u4eec\u7684\u6bcf\u4e2a\u9879\u76ee\u6dfb\u52a0\u5230 `result` \u5217\u8868\u4e2d\uff0c\u5e76\u5728\u4efb\u4e00\u53ef\u8fed\u4ee3\u5bf9\u8c61\u8017\u5c3d\u65f6\u505c\u6b62\u3002\n",
        "- \u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5f53\u4efb\u4e00\u53ef\u8fed\u4ee3\u5bf9\u8c61\u7528\u5c3d\u65f6\uff0c`result` \u5217\u8868\u4e2d\u7684\u73b0\u6709\u5143\u7d20\u5c06\u88ab\u4e22\u5f03\u3002\u8fd9\u5c31\u662f `numbers_iter` \u4e2d\u7684 `3` \u6240\u53d1\u751f\u7684\u60c5\u51b5\u3002\n",
        "- \u4f7f\u7528 zip \u6267\u884c\u4e0a\u8ff0\u64cd\u4f5c\u7684\u6b63\u786e\u65b9\u6cd5\u662f:\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    [(0, 0), (1, 1), (2, 2)]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    numbers = list(range(7))\n",
        "    numbers_iter = iter(numbers)\n",
        "    list(zip(first_three, numbers_iter))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    [(3, 3), (4, 4), (5, 5), (6, 6)]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    list(zip(remaining, numbers_iter))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "    `zip` \u7684\u7b2c\u4e00\u4e2a\u53c2\u6570\u5e94\u5f53\u662f\u6709\u6700\u5c11\u5143\u7d20\u7684\u90a3\u4e2a\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Loop variables leaking out!/\u5faa\u73af\u53d8\u91cf\u6cc4\u6f0f!\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": []
        }
      ],
      "source": [
        "for x in range(7):\n",
        "    if x == 6:\n",
        "        print(x, ': for x inside loop')\n",
        "print(x, ': x in global')\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "6 : for x inside loop\n",
        "6 : x in global\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4f46\u662f `x` \u4ece\u672a\u5728\u5faa\u73af\u5916\u88ab\u5b9a\u4e49...\n",
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": []
        }
      ],
      "source": [
        "# \u8fd9\u6b21\u6211\u4eec\u5148\u521d\u59cb\u5316x\n",
        "x = -1\n",
        "for x in range(7):\n",
        "    if x == 6:\n",
        "        print(x, ': for x inside loop')\n",
        "print(x, ': x in global')\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "6 : for x inside loop\n",
        "6 : x in global\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n",
        "```\n",
        "x = 1\n",
        "print([x for x in range(5)])\n",
        "print(x, ': x in global')\n",
        "```\n",
        "\n",
        "**Output (on Python 2.x):**\n",
        "```\n",
        "[0, 1, 2, 3, 4]\n",
        "(4, ': x in global')\n",
        "```\n",
        "\n",
        "**Output (on Python 3.x):**\n",
        "```\n",
        "[0, 1, 2, 3, 4]\n",
        "1 : x in global\n",
        "```\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- \u5728 Python \u4e2d, for \u5faa\u73af\u4f7f\u7528\u6240\u5728\u4f5c\u7528\u57df\u5e76\u5728\u7ed3\u675f\u540e\u4fdd\u7559\u5b9a\u4e49\u7684\u5faa\u73af\u53d8\u91cf. \u5982\u679c\u6211\u4eec\u66fe\u5728\u5168\u5c40\u547d\u540d\u7a7a\u95f4\u4e2d\u5b9a\u4e49\u8fc7\u5faa\u73af\u53d8\u91cf. \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b, \u5b83\u4f1a\u91cd\u65b0\u7ed1\u5b9a\u73b0\u6709\u53d8\u91cf.\n",
        "\n",
        "- Python 2.x \u548c Python 3.x \u89e3\u91ca\u5668\u5728\u5217\u8868\u63a8\u5bfc\u5f0f\u793a\u4f8b\u4e2d\u7684\u8f93\u51fa\u5dee\u5f02, \u5728\u6587\u6863 [What\u2019s New In Python 3.0](https://docs.python.org/3/whatsnew/3.0.html) \u4e2d\u53ef\u4ee5\u627e\u5230\u76f8\u5173\u7684\u89e3\u91ca:\n",
        "\n",
        "    > \"\u5217\u8868\u63a8\u5bfc\u4e0d\u518d\u652f\u6301\u53e5\u6cd5\u5f62\u5f0f `[... for var in item1, item2, ...]`. \u53d6\u800c\u4ee3\u4e4b\u7684\u662f `[... for var in (item1, item2, ...)]`. \u53e6\u5916, \u6ce8\u610f\u5217\u8868\u63a8\u5bfc\u5177\u6709\u4e0d\u540c\u7684\u8bed\u4e49: \u5b83\u4eec\u66f4\u63a5\u8fd1\u4e8e `list()` \u6784\u9020\u51fd\u6570\u4e2d\u751f\u6210\u5668\u8868\u8fbe\u5f0f\u7684\u8bed\u6cd5\u7cd6(\u8bd1: \u8fd9\u4e00\u53e5\u6211\u4e5f\u4e0d\u662f\u5f88\u660e\u767d), \u7279\u522b\u662f\u5faa\u73af\u63a7\u5236\u53d8\u91cf\u4e0d\u518d\u6cc4\u6f0f\u5230\u5468\u56f4\u7684\u4f5c\u7528\u57df\u4e2d.\"\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Beware of default mutable arguments!/\u5f53\u5fc3\u9ed8\u8ba4\u7684\u53ef\u53d8\u53c2\u6570!\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_func(default_arg=[]):\n",
        "    default_arg.append(\"some_string\")\n",
        "    return default_arg\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['some_string']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['some_string', 'some_string']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['some_string']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func([])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['some_string', 'some_string', 'some_string']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "- Python\u4e2d\u51fd\u6570\u7684\u9ed8\u8ba4\u53ef\u53d8\u53c2\u6570\u5e76\u4e0d\u662f\u6bcf\u6b21\u8c03\u7528\u8be5\u51fd\u6570\u65f6\u90fd\u4f1a\u88ab\u521d\u59cb\u5316. \u76f8\u53cd, \u5b83\u4eec\u4f1a\u4f7f\u7528\u6700\u8fd1\u5206\u914d\u7684\u503c\u4f5c\u4e3a\u9ed8\u8ba4\u503c. \u5f53\u6211\u4eec\u660e\u786e\u7684\u5c06 `[]` \u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9 `some_func` \u7684\u65f6\u5019, \u5c31\u4e0d\u4f1a\u4f7f\u7528 `default_arg` \u7684\u9ed8\u8ba4\u503c, \u6240\u4ee5\u51fd\u6570\u4f1a\u8fd4\u56de\u6211\u4eec\u6240\u671f\u671b\u7684\u7ed3\u679c.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    def some_func(default_arg=[]):\n",
        "        default_arg.append(\"some_string\")\n",
        "        return default_arg\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "    **Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    ([],)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_func.__defaults__ # \u8fd9\u91cc\u4f1a\u663e\u793a\u51fd\u6570\u7684\u9ed8\u8ba4\u53c2\u6570\u7684\u503c\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    (['some_string'],)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_func()\n",
        "    some_func.__defaults__\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    (['some_string', 'some_string'],)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_func()\n",
        "    some_func.__defaults__\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    (['some_string', 'some_string'],)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    some_func([])\n",
        "    some_func.__defaults__\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u907f\u514d\u53ef\u53d8\u53c2\u6570\u5bfc\u81f4\u7684\u9519\u8bef\u7684\u5e38\u89c1\u505a\u6cd5\u662f\u5c06 `None` \u6307\u5b9a\u4e3a\u53c2\u6570\u7684\u9ed8\u8ba4\u503c, \u7136\u540e\u68c0\u67e5\u662f\u5426\u6709\u503c\u4f20\u7ed9\u5bf9\u5e94\u7684\u53c2\u6570. \u4f8b:\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    def some_func(default_arg=None):\n",
        "        if not default_arg:\n",
        "            default_arg = []\n",
        "        default_arg.append(\"some_string\")\n",
        "        return default_arg\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Catching the Exceptions/\u6355\u83b7\u5f02\u5e38\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_list = [1, 2, 3]\n",
        "try:\n",
        "    # \u8fd9\u91cc\u4f1a\u629b\u51fa\u5f02\u5e38 ``IndexError``\n",
        "    print(some_list[4])\n",
        "except IndexError, ValueError:\n",
        "    print(\"Caught!\")\n",
        "\n",
        "try:\n",
        "    # \u8fd9\u91cc\u4f1a\u629b\u51fa\u5f02\u5e38 ``ValueError``\n",
        "    some_list.remove(4)\n",
        "except IndexError, ValueError:\n",
        "    print(\"Caught again!\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Caught!\n",
        "\n",
        "ValueError: list.remove(x): x not in list\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  File \"<input>\", line 3\n",
        "    except IndexError, ValueError:\n",
        "                     ^\n",
        "SyntaxError: invalid syntax\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u5982\u679c\u4f60\u60f3\u8981\u540c\u65f6\u6355\u83b7\u591a\u4e2a\u4e0d\u540c\u7c7b\u578b\u7684\u5f02\u5e38\u65f6, \u4f60\u9700\u8981\u5c06\u5b83\u4eec\u7528\u62ec\u53f7\u5305\u6210\u4e00\u4e2a\u5143\u7ec4\u4f5c\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\u4f20\u9012. \u7b2c\u4e8c\u4e2a\u53c2\u6570\u662f\u53ef\u9009\u540d\u79f0, \u5982\u679c\u4f60\u63d0\u4f9b, \u5b83\u5c06\u4e0e\u88ab\u6355\u83b7\u7684\u5f02\u5e38\u5b9e\u4f8b\u7ed1\u5b9a. \u4f8b,\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list = [1, 2, 3]\n",
        "  try:\n",
        "     # \u8fd9\u91cc\u4f1a\u629b\u51fa\u5f02\u5e38 ``ValueError``\n",
        "     some_list.remove(4)\n",
        "  except (IndexError, ValueError), e:\n",
        "     print(\"Caught again!\")\n",
        "     print(e)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  **Output (Python 2.x):**\n",
        "  ```\n",
        "  Caught again!\n",
        "  list.remove(x): x not in list\n",
        "  ```\n",
        "  **Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    File \"<input>\", line 4\n",
        "      except (IndexError, ValueError), e:\n",
        "                                       ^\n",
        "  IndentationError: unindent does not match any outer indentation level\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5728 Python 3 \u4e2d, \u7528\u9017\u53f7\u533a\u5206\u5f02\u5e38\u4e0e\u53ef\u9009\u540d\u79f0\u662f\u65e0\u6548\u7684; \u6b63\u786e\u7684\u505a\u6cd5\u662f\u4f7f\u7528 `as` \u5173\u952e\u5b57. \u4f8b,\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  some_list = [1, 2, 3]\n",
        "  try:\n",
        "      some_list.remove(4)\n",
        "\n",
        "  except (IndexError, ValueError) as e:\n",
        "      print(\"Caught again!\")\n",
        "      print(e)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "  **Output:**\n",
        "  ```\n",
        "  Caught again!\n",
        "  list.remove(x): x not in list\n",
        "  ```\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Same operands, different story!/\u540c\u4eba\u4e0d\u540c\u547d!\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = [1, 2, 3, 4]\n",
        "b = a\n",
        "a = a + [5, 6, 7, 8]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[1, 2, 3, 4, 5, 6, 7, 8]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[1, 2, 3, 4]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = [1, 2, 3, 4]\n",
        "b = a\n",
        "a += [5, 6, 7, 8]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[1, 2, 3, 4, 5, 6, 7, 8]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[1, 2, 3, 4, 5, 6, 7, 8]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "b\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "*  `a += b` \u5e76\u4e0d\u603b\u662f\u4e0e `a = a + b` \u8868\u73b0\u76f8\u540c. \u7c7b\u5b9e\u73b0 *`op=`* \u8fd0\u7b97\u7b26\u7684\u65b9\u5f0f *\u4e5f\u8bb8* \u662f\u4e0d\u540c\u7684, \u5217\u8868\u5c31\u662f\u8fd9\u6837\u505a\u7684.\n",
        "\n",
        "* \u8868\u8fbe\u5f0f `a = a + [5,6,7,8]` \u4f1a\u751f\u6210\u4e00\u4e2a\u65b0\u5217\u8868, \u5e76\u8ba9 `a` \u5f15\u7528\u8fd9\u4e2a\u65b0\u5217\u8868, \u540c\u65f6\u4fdd\u6301 `b` \u4e0d\u53d8.\n",
        "\n",
        "* \u8868\u8fbe\u5f0f `a += [5,6,7,8]` \u5b9e\u9645\u4e0a\u662f\u4f7f\u7528\u7684\u662f \"extend\" \u51fd\u6570, \u6240\u4ee5 `a` \u548c `b` \u4ecd\u7136\u6307\u5411\u5df2\u88ab\u4fee\u6539\u7684\u540c\u4e00\u5217\u8868.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Name resolution ignoring class scope/\u5ffd\u7565\u7c7b\u4f5c\u7528\u57df\u7684\u540d\u79f0\u89e3\u6790\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = 5\n",
        "class SomeClass:\n",
        "    x = 17\n",
        "    y = (x for i in range(10))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "5\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "list(SomeClass.y)[0]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = 5\n",
        "class SomeClass:\n",
        "    x = 17\n",
        "    y = [x for i in range(10)]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "17\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeClass.y[0]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "5\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeClass.y[0]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u7c7b\u5b9a\u4e49\u4e2d\u5d4c\u5957\u7684\u4f5c\u7528\u57df\u4f1a\u5ffd\u7565\u7c7b\u5185\u7684\u540d\u79f0\u7ed1\u5b9a.\n",
        "- \u751f\u6210\u5668\u8868\u8fbe\u5f0f\u6709\u5b83\u81ea\u5df1\u7684\u4f5c\u7528\u57df.\n",
        "- \u4ece Python 3.X \u5f00\u59cb, \u5217\u8868\u63a8\u5bfc\u5f0f\u4e5f\u6709\u81ea\u5df1\u7684\u4f5c\u7528\u57df.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Rounding like a banker/\u50cf\u94f6\u884c\u5bb6\u4e00\u6837\u820d\u5165 *\n",
        "\u8ba9\u6211\u4eec\u5b9e\u73b0\u4e00\u4e2a\u7b80\u5355\u7684\u51fd\u6570\u6765\u83b7\u53d6\u5217\u8868\u7684\u4e2d\u95f4\u5143\u7d20\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def get_middle(some_list):\n",
        "    mid_index = round(len(some_list) / 2)\n",
        "    return some_list[mid_index - 1]\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Python 3.x:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "get_middle([1])  # looks good\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "get_middle([1,2,3])  # looks good\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "get_middle([1,2,3,4,5])  # huh?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2.5\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len([1,2,3,4,5]) / 2  # good\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "round(len([1,2,3,4,5]) / 2)  # why?\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4f3c\u4e4e Python \u5c06 2.5 \u820d\u5165\u5230 2\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- - \u8fd9\u4e0d\u662f\u6d6e\u70b9\u7cbe\u5ea6\u9519\u8bef\uff0c\u5b9e\u9645\u4e0a\uff0c\u8fd9\u79cd\u884c\u4e3a\u662f\u6545\u610f\u7684\u3002\u4ece Python 3.0 \u5f00\u59cb\uff0c`round()` \u4f7f\u7528[\u94f6\u884c\u8fdb\u4f4d\u6cd5](https://en.wikipedia.org/wiki/Rounding#Round_half_to_even)\uff0c\u5176\u4e2d 0.5 \u5c0f\u6570\u56db\u820d\u4e94\u5165\u5230\u6700\u63a5\u8fd1\u7684 **\u5076\u6570** \uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "round(0.5)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "round(1.5)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "round(2.5)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0.0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import numpy  # numpy\u7684\u7ed3\u679c\u4e5f\u662f\u4e00\u6837\n",
        "numpy.round(0.5)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2.0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "numpy.round(1.5)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "2.0\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "numpy.round(2.5)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u8fd9\u662f [IEEE 754](https://en.wikipedia.org/wiki/IEEE_754#Rounding_rules) \u4e2d\u63cf\u8ff0\u7684\u5173\u4e8e0.5\u5206\u4f4d\u820d\u5165\u7684\u63a8\u8350\u65b9\u6cd5\u3002\u7136\u800c\uff0c\u53e6\u4e00\u79cd\u65b9\u6cd5\uff08\u4ece\u96f6\u53d6\u6574\uff09\u5927\u90e8\u5206\u65f6\u95f4\u90fd\u662f\u5728\u5b66\u6821\u6559\u6388\u7684\uff0c\u6240\u4ee5\u94f6\u884c\u8fdb\u4f4d\u6cd5\u53ef\u80fd\u5e76\u4e0d\u4e3a\u4eba\u6240\u77e5\u3002\u6b64\u5916\uff0c\u4e00\u4e9b\u6700\u6d41\u884c\u7684\u7f16\u7a0b\u8bed\u8a00\uff08\u4f8b\u5982\uff1aJavaScript\u3001Java\u3001C/C++\u3001Ruby\u3001Rust\uff09\u4e5f\u4e0d\u4f7f\u7528\u94f6\u884c\u8fdb\u4f4d\u6cd5\u3002\u56e0\u6b64\uff0c\u8fd9\u5bf9 Python \u6765\u8bf4\u8fd8\u662f\u6bd4\u8f83\u7279\u6b8a\u7684\uff0c\u5728\u56db\u820d\u4e94\u5165\u65f6\u53ef\u80fd\u4f1a\u5bfc\u81f4\u6df7\u6dc6\u3002\n",
        "- \u4e86\u89e3\u66f4\u591a\u4fe1\u606f\uff0c\u8bf7\u53c2\u9605\u6587\u6863 [round()](https://docs.python.org/3/library/functions.html#round) \u6216 [this stackoverflow thread](https://stackoverflow.com/questions/10825926/python -3-x-rounding-behavior) \n",
        "- \u8bf7\u6ce8\u610f\uff0c`get_middle([1])` \u53ea\u8fd4\u56de1\uff0c\u56e0\u4e3a\u5b83\u7684\u7d22\u5f15\u662f `round(0.5) - 1 = 0 - 1 = -1`\uff0c\u8fd4\u56de\u5217\u8868\u4e2d\u7684\u6700\u540e\u4e00\u4e2a\u5143\u7d20\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Needles in a Haystack/\u5927\u6d77\u635e\u9488\n",
        "\u8fc4\u4eca\u4e3a\u6b62\uff0c\u6bcf\u4e00\u4f4dPython\u5f00\u53d1\u8005\u90fd\u4f1a\u9047\u5230\u7c7b\u4f3c\u4ee5\u4e0b\u7684\u60c5\u51b5\u3002\n",
        "\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x, y = (0, 1) if True else None, None\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "```\n",
        ">>> x, y  # \u671f\u671b\u7684\u7ed3\u679c\u662f (0, 1)\n",
        "((0, 1), None)\n",
        "```\n",
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": []
        }
      ],
      "source": [
        "t = ('one', 'two')\n",
        "for i in t:\n",
        "    print(i)\n",
        "\n",
        "t = ('one')\n",
        "for i in t:\n",
        "    print(i)\n",
        "\n",
        "t = ()\n",
        "print(t)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "one\n",
        "two\n",
        "o\n",
        "n\n",
        "e\n",
        "tuple()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "3\\.\n",
        "\n",
        "```\n",
        "ten_words_list = [\n",
        "    \"some\",\n",
        "    \"very\",\n",
        "    \"big\",\n",
        "    \"list\",\n",
        "    \"that\"\n",
        "    \"consists\",\n",
        "    \"of\",\n",
        "    \"exactly\",\n",
        "    \"ten\",\n",
        "    \"words\"\n",
        "]\n",
        "```\n",
        "\n",
        "**Output**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "9\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len(ten_words_list)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "4\\. \u4e0d\u591f\u5065\u58ee\u7684\u65ad\u8a00\u673a\u5236\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "a = \"python\"\n",
        "b = \"javascript\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "# \u672a\u5f15\u53d1 AssertionError \n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# \u5e26\u6709\u5931\u8d25\u8b66\u544a\u4fe1\u606f\u7684assert\u8868\u8fbe\u5f0f\n",
        "assert(a == b, \"Both languages are different\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "5\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_list = [1, 2, 3]\n",
        "some_dict = {\n",
        "  \"key_1\": 1,\n",
        "  \"key_2\": 2,\n",
        "  \"key_3\": 3\n",
        "}\n",
        "\n",
        "some_list = some_list.append(4) \n",
        "some_dict = some_dict.update({\"key_4\": 4})\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "None\n"
          ]
        }
      ],
      "source": [
        "print(some_list)\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": [
            "None\n"
          ]
        }
      ],
      "source": [
        "print(some_dict)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "6\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_recursive_func(a):\n",
        "    if a[0] == 0:\n",
        "        return\n",
        "    a[0] -= 1\n",
        "    some_recursive_func(a)\n",
        "    return a\n",
        "\n",
        "def similar_recursive_func(a):\n",
        "    if a == 0:\n",
        "        return a\n",
        "    a -= 1\n",
        "    similar_recursive_func(a)\n",
        "    return a\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "[0, 0]\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_recursive_func([5, 0])\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "4\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "similar_recursive_func(5)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "* \u5bf9\u4e8e 1, \u6b63\u786e\u7684\u8bed\u53e5\u662f `x, y = (0, 1) if True else (None, None)`.\n",
        "* \u5bf9\u4e8e 2, \u6b63\u786e\u7684\u8bed\u53e5\u662f `t = ('one',)` \u6216\u8005 `t = 'one',` (\u7f3a\u5c11\u9017\u53f7) \u5426\u5219\u89e3\u91ca\u5668\u4f1a\u8ba4\u4e3a `t` \u662f\u4e00\u4e2a\u5b57\u7b26\u4e32, \u5e76\u9010\u4e2a\u5b57\u7b26\u5bf9\u5176\u8fdb\u884c\u8fed\u4ee3.\n",
        "* `()` \u662f\u4e00\u4e2a\u7279\u6b8a\u7684\u6807\u8bb0\uff0c\u8868\u793a\u7a7a\u5143\u7ec4.\n",
        "* \u5bf9\u4e8e 3\uff0c\u6b63\u5982\u60a8\u53ef\u80fd\u5df2\u7ecf\u5f04\u6e05\u695a\u7684\u90a3\u6837\uff0c\u5217\u8868\u4e2d\u7684\u7b2c5\u4e2a\u5143\u7d20\uff08\"that\"\uff09\u540e\u9762\u7f3a\u5c11\u4e00\u4e2a\u9017\u53f7\u3002\u56e0\u6b64\uff0c\u901a\u8fc7\u9690\u5f0f\u5b57\u7b26\u4e32\u5b57\u9762\u8fde\u63a5\uff0c\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  ['some', 'very', 'big', 'list', 'thatconsists', 'of', 'exactly', 'ten', 'words']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  ten_words_list\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "* \u5728\u7b2c4\u4e2a\u4ee3\u7801\u6bb5\u4e2d\u6ca1\u6709\u5f15\u53d1\"AssertionError\"\uff0c\u56e0\u4e3a\u6211\u4eec\u4e0d\u662f\u65ad\u8a00\u5355\u4e2a\u8868\u8fbe\u5f0f `a == b`\uff0c\u800c\u662f\u65ad\u8a00\u6574\u4e2a\u5143\u7ec4\u3002\u4ee5\u4e0b\u4ee3\u7801\u6bb5\u5c06\u8bf4\u660e\u95ee\u9898\uff0c\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  Traceback (most recent call last):\n",
              "      File \"<stdin>\", line 1, in <module>\n",
              "  AssertionError\n",
              "  \n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  a = \"python\"\n",
        "  b = \"javascript\"\n",
        "  assert a == b\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  <stdin>:1: SyntaxWarning: assertion is always true, perhaps remove parentheses?\n",
              "  \n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  assert (a == b, \"Values are not equal\")\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  Traceback (most recent call last):\n",
              "      File \"<stdin>\", line 1, in <module>\n",
              "  AssertionError: Values are not equal\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  assert a == b, \"Values are not equal\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "* \u81f3\u4e8e\u7b2c\u4e94\u4e2a\u7247\u6bb5\uff0c\u5927\u591a\u6570\u4fee\u6539\u5e8f\u5217/\u6620\u5c04\u5bf9\u8c61\u9879\u7684\u65b9\u6cd5\uff0c\u5982`list.append`\u3001`dict.update`\u3001`list.sort`\u7b49\uff0c\u90fd\u5728\u539f\u5730\u4fee\u6539\u5bf9\u8c61\u5e76\u8fd4\u56de`None`\u3002\u8fd9\u80cc\u540e\u7684\u57fa\u672c\u539f\u7406\u662f\u901a\u8fc7\u539f\u5730\u64cd\u4f5c\uff0c\u907f\u514d\u590d\u5236\u5bf9\u8c61\u6765\u63d0\u9ad8\u6027\u80fd(\u53c2\u8003[\u8fd9\u91cc](https://docs.python.org/3/faq/design.html#why-doesn-t-list-sort-return-the-sorted-list))\u3002\n",
        "* \u6700\u540e\u4e00\u4e2a\u5e94\u8be5\u76f8\u5f53\u660e\u663e\uff0c\u53ef\u53d8\u5bf9\u8c61\uff08\u5982`list`\uff09\u53ef\u4ee5\u5728\u51fd\u6570\u4e2d\u66f4\u6539\uff0c\u4e0d\u53ef\u53d8\u5bf9\u8c61\uff08`a -= 1`\uff09\u7684\u91cd\u65b0\u8d4b\u503c\u5219\u4e0d\u5c5e\u4e8e\u503c\u7684\u6539\u53d8\u3002\n",
        "* \u4e86\u89e3\u8fd9\u4e9b\u7ec6\u8282\u53ef\u4ee5\u5728\u7a0b\u5e8f\u957f\u671f\u8fd0\u884c\u4e2d\uff0c\u4e3a\u60a8\u8282\u7701\u6570\u5c0f\u65f6\u7684\u8c03\u8bd5\u5de5\u4f5c\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Splitsies/\u5206\u5272\u51fd\u6570 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a']\n",
              "\n",
              "# is same as\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'a'.split()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "['a']\n",
              "\n",
              "# but\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'a'.split(' ')\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0\n",
              "\n",
              "# isn't the same as\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len(''.split())\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "len(''.split(' '))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- \u8d77\u521d\u4eba\u4eec\u53ef\u80fd\u4f1a\u8ba4\u4e3a split \u7684\u9ed8\u8ba4\u5206\u9694\u7b26\u662f\u5355\u4e2a\u7a7a\u683c `' '`\uff0c\u4f46\u6839\u636e [\u6587\u6863](https://docs.python.org/3/library/stdtypes.html#str.split)\uff1a\n",
        "    >  \u5982\u679c sep \u672a\u6307\u5b9a\u6216\u4e3a `None`\uff0c\u5219\u5e94\u7528\u4e0d\u540c\u7684\u62c6\u5206\u7b97\u6cd5\uff1a\u8fde\u7eed\u7684\u7a7a\u683c\u88ab\u89c6\u4e3a\u5355\u4e2a\u5206\u9694\u7b26\uff0c\u5982\u679c\u5b57\u7b26\u4e32\u6709\u524d\u5bfc\u6216\u5c3e\u968f\u7a7a\u683c\uff0c\u5219\u7ed3\u679c\u5c06\u5728\u5f00\u5934\u6216\u7ed3\u5c3e\u4e0d\u5305\u542b\u7a7a\u5b57\u7b26\u4e32\u3002\u56e0\u6b64\uff0c\u4f7f\u7528 `None` \u5206\u9694\u7b26\u62c6\u5206\u7a7a\u5b57\u7b26\u4e32\u6216\u4ec5\u5305\u542b\u7a7a\u683c\u7684\u5b57\u7b26\u4e32\u5c06\u8fd4\u56de `[]`\u3002\n",
        "    > \u5982\u679c\u7ed9\u5b9a sep\uff0c\u8fde\u7eed\u7684\u5206\u9694\u7b26\u4e0d\u4f1a\u7ec4\u5408\u5728\u4e00\u8d77\uff0c\u5e76\u88ab\u89c6\u4e3a\u5206\u9694\u7a7a\u5b57\u7b26\u4e32\uff08\u4f8b\u5982\uff0c`'1,,2'.split(',')` \u8fd4\u56de `['1', '', '2 ']`\uff09\u3002\u4f7f\u7528\u6307\u5b9a\u7684\u5206\u9694\u7b26\u62c6\u5206\u7a7a\u5b57\u7b26\u4e32\u4f1a\u8fd4\u56de `['']`\u3002\n",
        "- Noticing how the leading and trailing whitespaces are handled in the following snippet will make things clear,\n",
        "- \u6ce8\u610f\u4ee5\u4e0b\u4ee3\u7801\u6bb5\u4e2d\u5982\u4f55\u5904\u7406\u524d\u5bfc\u548c\u5c3e\u968f\u7a7a\u683c\uff0c\u4fc3\u8fdb\u66f4\u6df1\u5165\u7684\u7406\u89e3\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    ['', 'a', '']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    ' a '.split(' ')\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    ['a']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    ' a '.split()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    ['']\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    ''.split(' ')\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > All sorted?/\u90fd\u6392\u5e8f\u4e86\u5417\uff1f *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "x = 7, 8, 9\n",
        "sorted(x) == x\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "sorted(x) == sorted(x)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "y = reversed(x)\n",
        "sorted(y) == sorted(y)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- `sorted` \u65b9\u6cd5\u4e00\u5b9a\u8fd4\u56de\u5217\u8868\u7c7b\u578b, \u6bd4\u8f83\u5217\u8868\u4e0e\u5143\u7ec4\u5728Python\u4e2d\u4e00\u5b9a\u8fd4\u56de `False`. \n",
        "\n",
        "- ```py\n",
        "  >>> [] == tuple()\n",
        "  False\n",
        "  >>> x = 7, 8, 9\n",
        "  >>> type(x), type(sorted(x))\n",
        "  (tuple, list)\n",
        "  ```\n",
        "\n",
        "- \u4e0e `sorted` \u4e0d\u540c\uff0c`reversed` \u65b9\u6cd5\u8fd4\u56de\u4e00\u4e2a\u8fed\u4ee3\u5668\u3002\u4e3a\u4ec0\u4e48\uff1f\u56e0\u4e3a\u6392\u5e8f\u9700\u8981\u5c31\u5730\u4fee\u6539\u8fed\u4ee3\u5668\u6216\u4f7f\u7528\u989d\u5916\u7684\u5bb9\u5668\uff08\u5217\u8868\uff09\uff0c\u800c\u53cd\u5411\u53ef\u4ee5\u7b80\u5355\u5730\u901a\u8fc7\u4ece\u6700\u540e\u4e00\u4e2a\u7d22\u5f15\u8fed\u4ee3\u5230\u7b2c\u4e00\u4e2a\u7d22\u5f15\u6765\u5de5\u4f5c\u3002\n",
        "\n",
        "- \u6240\u4ee5\u5728\u6bd4\u8f83 `sorted(y) == sorted(y)` \u65f6\uff0c\u7b2c\u4e00\u6b21\u8c03\u7528 `sorted()` \u4f1a\u6d88\u8017\u8fed\u4ee3\u5668 `y`\uff0c\u4e0b\u4e00\u6b21\u8c03\u7528\u53ea\u4f1a\u8fd4\u56de\u4e00\u4e2a\u7a7a\u5217\u8868\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  ([7, 8, 9], [])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  x = 7, 8, 9\n",
        "  y = reversed(x)\n",
        "  sorted(y), sorted(y)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Midnight time doesn't exist?/\u4e0d\u5b58\u5728\u7684\u5348\u591c?\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "from datetime import datetime\n",
        "\n",
        "midnight = datetime(2018, 1, 1, 0, 0)\n",
        "midnight_time = midnight.time()\n",
        "\n",
        "noon = datetime(2018, 1, 1, 12, 0)\n",
        "noon_time = noon.time()\n",
        "\n",
        "if midnight_time:\n",
        "    print(\"Time at midnight is\", midnight_time)\n",
        "\n",
        "if noon_time:\n",
        "    print(\"Time at noon is\", noon_time)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "```sh\n",
        "('Time at noon is', datetime.time(12, 0))\n",
        "```\n",
        "\n",
        "midnight_time \u5e76\u6ca1\u6709\u88ab\u8f93\u51fa.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "\u5728Python 3.5\u4e4b\u524d, \u5982\u679c `datetime.time` \u5bf9\u8c61\u5b58\u50a8\u7684UTC\u7684\u5348\u591c\u65f6\u95f4(\u8bd1: \u5c31\u662f `00:00`), \u90a3\u4e48\u5b83\u7684\u5e03\u5c14\u503c\u4f1a\u88ab\u8ba4\u4e3a\u662f `False`. \u5f53\u4f7f\u7528 `if obj:` \u8bed\u53e5\u6765\u68c0\u67e5 `obj` \u662f\u5426\u4e3a `null` \u6216\u8005\u67d0\u4e9b\u201c\u7a7a\u201d\u503c\u7684\u65f6\u5019, \u5f88\u5bb9\u6613\u51fa\u9519.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Okay Python, Can you make me fly?/Python, \u53ef\u5426\u5e26\u6211\u98de? *\n",
        "\u597d, \u53bb\u5427.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import antigravity\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n",
        "\u5618.. \u8fd9\u662f\u4e2a\u8d85\u7ea7\u79d8\u5bc6.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "+ `antigravity` \u6a21\u5757\u662f Python \u5f00\u53d1\u4eba\u5458\u53d1\u5e03\u7684\u5c11\u6570\u590d\u6d3b\u8282\u5f69\u86cb\u4e4b\u4e00.\n",
        "+ `import antigravity` \u4f1a\u6253\u5f00\u4e00\u4e2a Python \u7684[\u7ecf\u5178 XKCD \u6f2b\u753b](http://xkcd.com/353/)\u9875\u9762.\n",
        "+ \u4e0d\u6b62\u5982\u6b64. \u8fd9\u4e2a**\u590d\u6d3b\u8282\u5f69\u86cb\u91cc\u8fd8\u6709\u4e00\u4e2a\u590d\u6d3b\u8282\u5f69\u86cb**. \u5982\u679c\u4f60\u770b\u4e00\u4e0b[\u4ee3\u7801](https://github.com/python/cpython/blob/master/Lib/antigravity.py#L7-L17), \u5c31\u4f1a\u53d1\u73b0\u8fd8\u6709\u4e00\u4e2a\u51fd\u6570\u5b9e\u73b0\u4e86 [XKCD's geohashing \u7b97\u6cd5](https://xkcd.com/426/).\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > `goto`, but why?/`goto`, \u4f46\u4e3a\u4ec0\u4e48? *\n"
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "collapsed": true
      },
      "execution_count": null,
      "outputs": [
        {
          "name": "stdout",
          "output_type": "stream",
          "text": []
        }
      ],
      "source": [
        "from goto import goto, label\n",
        "for i in range(9):\n",
        "    for j in range(9):\n",
        "        for k in range(9):\n",
        "            print(\"I'm trapped, please rescue!\")\n",
        "            if k == 2:\n",
        "                goto .breakout # \u4ece\u591a\u91cd\u5faa\u73af\u4e2d\u8df3\u51fa\n",
        "label .breakout\n",
        "print(\"Freedom!\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.3):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "I'm trapped, please rescue!\n",
        "I'm trapped, please rescue!\n",
        "Freedom!\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- 2004\u5e744\u67081\u65e5, Python [\u5ba3\u5e03](https://mail.python.org/pipermail/python-announce-list/2004-April/002982.html) \u52a0\u5165\u4e00\u4e2a\u53ef\u7528\u7684 `goto` \u4f5c\u4e3a\u611a\u4eba\u8282\u793c\u7269.\n",
        "- \u5f53\u524d\u7248\u672c\u7684 Python \u5e76\u6ca1\u6709\u8fd9\u4e2a\u6a21\u5757.\n",
        "- \u5c31\u7b97\u53ef\u4ee5\u7528, \u4e5f\u8bf7\u4e0d\u8981\u4f7f\u7528\u5b83. \u8fd9\u91cc\u662f\u4e3a\u4ec0\u4e48Python\u4e2d\u6ca1\u6709 `goto` \u7684[\u539f\u56e0](https://docs.python.org/3/faq/design.html#why-is-there-no-goto).\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Brace yourself!/\u505a\u597d\u601d\u60f3\u51c6\u5907 *\n",
        "\u5982\u679c\u4f60\u4e0d\u559c\u6b22\u5728Python\u4e2d\u4f7f\u7528\u7a7a\u683c\u6765\u8868\u793a\u4f5c\u7528\u57df, \u4f60\u53ef\u4ee5\u5bfc\u5165 C \u98ce\u683c\u7684 {},\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "from __future__ import braces\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  File \"some_file.py\", line 1\n",
        "    from __future__ import braces\n",
        "SyntaxError: not a chance\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u60f3\u7528\u5927\u62ec\u53f7 `braces`? \u6ca1\u95e8! \u89c9\u5f97\u4e0d\u723d, \u8bf7\u53bb\u7528java\u3002\u90a3\u4e48\uff0c\u53e6\u4e00\u4e2a\u4ee4\u4eba\u60ca\u8bb6\u7684\u4e8b\u60c5\uff0c\u627e\u4e00\u627e\u5728 `__future__` \u6a21\u5757\u4e2d\uff0c\u54ea\u91cc\u5f15\u53d1\u4e86 `SyntaxError` [code](https://github.com/python/cpython/blob/master/Lib/__future__.py)?\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "+ \u901a\u5e38 `__future__` \u4f1a\u63d0\u4f9b Python \u672a\u6765\u7248\u672c\u7684\u529f\u80fd. \u7136\u800c\uff0c\u8fd9\u91cc\u7684 \u201c\u672a\u6765\u201d \u662f\u4e00\u4e2a\u8bbd\u523a.\n",
        "+ \u8fd9\u662f\u4e00\u4e2a\u8868\u8fbe\u793e\u533a\u5bf9\u6b64\u7c7b\u95ee\u9898\u6001\u5ea6\u7684\u590d\u6d3b\u8282\u5f69\u86cb.\n",
        "+ \u4ee3\u7801\u5b9e\u9645\u4e0a\u5728[`future.c` \u6587\u4ef6]\u4e2d (https://github.com/python/cpython/blob/025eb98dc0c1dc27404df6c544fc2944e0fa9f3a/Python/future.c#L49).\n",
        "+ \u5f53 CPython \u7f16\u8bd1\u5668\u9047\u5230 [future\u8868\u8fbe\u5f0f](https://docs.python.org/3.3/reference/simple_stmts.html#future-statements) \u65f6\uff0c\u5b83\u9996\u5148\u5728 `future.c` \u4e2d\u8fd0\u884c\u76f8\u5e94\u7684\u4ee3\u7801\uff0c\u7136\u540e\u518d\u5bf9\u5176\u8fdb\u884c\u5904\u7406\u4f5c\u4e3a\u6b63\u5e38\u7684`import`\u8868\u8fbe\u5f0f\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Let's meet Friendly Language Uncle For Life/\u8ba9\u751f\u6d3b\u66f4\u53cb\u597d *\n",
        "**Output (Python 3.x)**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  File \"some_file.py\", line 1\n",
              "    \"Ruby\" != \"Python\"\n",
              "              ^\n",
              "SyntaxError: invalid syntax\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "from __future__ import barry_as_FLUFL\n",
        "\"Ruby\" != \"Python\" # \u8fd9\u91cc\u6ca1\u4ec0\u4e48\u7591\u95ee\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "\"Ruby\" <> \"Python\"\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8fd9\u5c31\u5bf9\u4e86.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u76f8\u5173\u7684 [PEP-401](https://www.python.org/dev/peps/pep-0401/) \u53d1\u5e03\u4e8e 2009\u5e744\u67081\u65e5 (\u6240\u4ee5\u4f60\u73b0\u5728\u77e5\u9053\u8fd9\u610f\u5473\u7740\u4ec0\u4e48\u4e86\u5427).\n",
        "- \u5f15\u7528 PEP-401\n",
        "  > \u610f\u8bc6\u5230 Python 3.0 \u91cc\u7684 != \u8fd0\u7b97\u7b26\u662f\u4e00\u4e2a\u4f1a\u5f15\u8d77\u624b\u6307\u75bc\u75db\u7684\u6050\u6016\u9519\u8bef, FLUFL \u5c06 <> \u8fd0\u7b97\u7b26\u6062\u590d\u4e3a\u552f\u4e00\u5199\u6cd5.\n",
        "- Uncle Barry \u5728 PEP \u4e2d\u8fd8\u5206\u4eab\u4e86\u5176\u4ed6\u4e1c\u897f; \u4f60\u53ef\u4ee5\u5728[\u8fd9\u91cc](https://www.python.org/dev/peps/pep-0401/)\u83b7\u5f97\u4ed6\u4eec.\n",
        "- (\u8bd1: \u867d\u7136\u6587\u6863\u4e2d\u6ca1\u5199\uff0c\u4f46\u5e94\u8be5\u662f\u53ea\u80fd\u5728\u4ea4\u4e92\u89e3\u91ca\u5668\u4e2d\u4f7f\u7528.)\n",
        "- \u5b83\u5728\u4ea4\u4e92\u5f0f\u73af\u5883\u4e2d\u6b63\u5e38\u8fd0\u884c\uff0c\u4f46\u662f\u5f53\u60a8\u901a\u8fc7 python \u6587\u4ef6\u8fd0\u884c\u65f6\u5b83\u4f1a\u5f15\u53d1 `SyntaxError`\uff08\u8bf7\u53c2\u9605\u6b64 [\u95ee\u9898](https://github.com/satwikkansal/wtfpython/issues/94)\uff09\u3002\u60a8\u53ef\u4ee5\u5c06\u8868\u8fbe\u5f0f\u4f5c\u4e3a`eval` \u6216 `compile` \u53c2\u6570\u4e2d\u4f7f\u7528\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    from __future__ import barry_as_FLUFL\n",
        "    print(eval('\"Ruby\" <> \"Python\"'))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Even Python understands that love is complicated/\u8fdePython\u4e5f\u77e5\u9053\u7231\u662f\u96be\u8a00\u7684 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import this\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u7b49\u7b49, **this** \u662f\u4ec0\u4e48? `this` \u662f\u7231 :heart:\n",
        "\n",
        "**Output:**\n",
        "```\n",
        "The Zen of Python, by Tim Peters\n",
        "\n",
        "Beautiful is better than ugly.\n",
        "\u4f18\u7f8e\u80dc\u4e8e\u4e11\u964b\uff08Python \u4ee5\u7f16\u5199\u4f18\u7f8e\u7684\u4ee3\u7801\u4e3a\u76ee\u6807\uff09\n",
        "Explicit is better than implicit.\n",
        "\u660e\u4e86\u80dc\u4e8e\u6666\u6da9\uff08\u4f18\u7f8e\u7684\u4ee3\u7801\u5e94\u5f53\u662f\u660e\u4e86\u7684\uff0c\u547d\u540d\u89c4\u8303\uff0c\u98ce\u683c\u76f8\u4f3c\uff09\n",
        "Simple is better than complex.\n",
        "\u7b80\u6d01\u80dc\u4e8e\u590d\u6742\uff08\u4f18\u7f8e\u7684\u4ee3\u7801\u5e94\u5f53\u662f\u7b80\u6d01\u7684\uff0c\u4e0d\u8981\u6709\u590d\u6742\u7684\u5185\u90e8\u5b9e\u73b0\uff09\n",
        "Complex is better than complicated.\n",
        "\u590d\u6742\u80dc\u4e8e\u51cc\u4e71\uff08\u5982\u679c\u590d\u6742\u4e0d\u53ef\u907f\u514d\uff0c\u90a3\u4ee3\u7801\u95f4\u4e5f\u4e0d\u80fd\u6709\u96be\u61c2\u7684\u5173\u7cfb\uff0c\u8981\u4fdd\u6301\u63a5\u53e3\u7b80\u6d01\uff09\n",
        "Flat is better than nested.\n",
        "\u6241\u5e73\u80dc\u4e8e\u5d4c\u5957\uff08\u4f18\u7f8e\u7684\u4ee3\u7801\u5e94\u5f53\u662f\u6241\u5e73\u7684\uff0c\u4e0d\u80fd\u6709\u592a\u591a\u7684\u5d4c\u5957\uff09\n",
        "Sparse is better than dense.\n",
        "\u95f4\u9694\u80dc\u4e8e\u7d27\u51d1\uff08\u4f18\u7f8e\u7684\u4ee3\u7801\u6709\u9002\u5f53\u7684\u95f4\u9694\uff0c\u4e0d\u8981\u5962\u671b\u4e00\u884c\u4ee3\u7801\u89e3\u51b3\u95ee\u9898\uff09\n",
        "Readability counts.\n",
        "\u53ef\u8bfb\u6027\u5f88\u91cd\u8981\uff08\u4f18\u7f8e\u7684\u4ee3\u7801\u4e00\u5b9a\u662f\u53ef\u8bfb\u7684\uff09\n",
        "Special cases aren't special enough to break the rules.\n",
        "\u6ca1\u6709\u7279\u4f8b\u7279\u6b8a\u5230\u9700\u8981\u8fdd\u80cc\u8fd9\u4e9b\u89c4\u5219\uff08\u8fd9\u4e9b\u89c4\u5219\u81f3\u9ad8\u65e0\u4e0a\uff09\n",
        "Although practicality beats purity.\n",
        "\u5c3d\u7ba1\u6211\u4eec\u66f4\u503e\u5411\u4e8e\u5b9e\u7528\u6027\n",
        "Errors should never pass silently.\n",
        "\u4e0d\u8981\u5b89\u9759\u7684\u5305\u5bb9\u6240\u6709\u9519\u8bef\n",
        "Unless explicitly silenced.\n",
        "\u9664\u975e\u4f60\u786e\u5b9a\u9700\u8981\u8fd9\u6837\u505a\uff08\u7cbe\u51c6\u5730\u6355\u83b7\u5f02\u5e38\uff0c\u4e0d\u5199 except:pass \u98ce\u683c\u7684\u4ee3\u7801\uff09\n",
        "In the face of ambiguity, refuse the temptation to guess.\n",
        "\u62d2\u7edd\u8bf1\u60d1\u4f60\u53bb\u731c\u6d4b\u7684\u66a7\u6627\u4e8b\u7269\n",
        "There should be one-- and preferably only one --obvious way to do it.\n",
        "\u800c\u662f\u5c3d\u91cf\u627e\u4e00\u79cd\uff0c\u6700\u597d\u662f\u552f\u4e00\u4e00\u79cd\u660e\u663e\u7684\u89e3\u51b3\u65b9\u6848\uff08\u5982\u679c\u4e0d\u786e\u5b9a\uff0c\u5c31\u7528\u7a77\u4e3e\u6cd5\uff09\n",
        "Although that way may not be obvious at first unless you're Dutch.\n",
        "\u867d\u7136\u8fd9\u5e76\u4e0d\u5bb9\u6613\uff0c\u56e0\u4e3a\u4f60\u4e0d\u662f Python \u4e4b\u7236\uff08\u8fd9\u91cc\u7684 Dutch \u662f\u6307 Guido \uff09\n",
        "Now is better than never.\n",
        "\u73b0\u5728\u884c\u52a8\u597d\u8fc7\u6c38\u8fdc\u4e0d\u884c\u52a8\n",
        "Although never is often better than *right* now.\n",
        "\u5c3d\u7ba1\u4e0d\u884c\u52a8\u8981\u597d\u8fc7\u9c81\u83bd\u884c\u52a8\n",
        "If the implementation is hard to explain, it's a bad idea.\n",
        "\u5982\u679c\u4f60\u65e0\u6cd5\u5411\u4eba\u63cf\u8ff0\u4f60\u7684\u65b9\u6848\uff0c\u90a3\u80af\u5b9a\u4e0d\u662f\u4e00\u4e2a\u597d\u65b9\u6848\uff1b\n",
        "If the implementation is easy to explain, it may be a good idea.\n",
        "\u5982\u679c\u4f60\u80fd\u8f7b\u677e\u5411\u4eba\u63cf\u8ff0\u4f60\u7684\u65b9\u6848\uff0c\u90a3\u4e5f\u8bb8\u4f1a\u662f\u4e00\u4e2a\u597d\u65b9\u6848\uff08\u65b9\u6848\u6d4b\u8bc4\u6807\u51c6\uff09\n",
        "Namespaces are one honking great idea -- let's do more of those!\n",
        "\u547d\u540d\u7a7a\u95f4\u662f\u4e00\u79cd\u7edd\u5999\u7684\u7406\u5ff5\uff0c\u6211\u4eec\u5e94\u5f53\u591a\u52a0\u5229\u7528\uff08\u5021\u5bfc\u4e0e\u53f7\u53ec\uff09\n",
        "```\n",
        "\n",
        "\u8fd9\u662f Python \u4e4b\u7985!\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "love = this\n",
        "this is love\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "love is True\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "love is False\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "love is not True or False\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "love is not True or False; love is love  # \u7231\u662f\u96be\u8a00\u7684\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* `this` \u6a21\u5757\u662f\u5173\u4e8e Python \u4e4b\u7985\u7684\u590d\u6d3b\u8282\u5f69\u86cb ([PEP 20](https://www.python.org/dev/peps/pep-0020)).\n",
        "* \u5982\u679c\u4f60\u8ba4\u4e3a\u8fd9\u5df2\u7ecf\u591f\u6709\u8da3\u7684\u4e86, \u53ef\u4ee5\u770b\u770b [this.py](https://hg.python.org/cpython/file/c3896275c0f6/Lib/this.py) \u7684\u5b9e\u73b0. \u6709\u8da3\u7684\u662f, Python \u4e4b\u7985\u7684\u5b9e\u73b0\u4ee3\u7801\u8fdd\u53cd\u4e86\u4ed6\u81ea\u5df1 (\u8fd9\u53ef\u80fd\u662f\u552f\u4e00\u4f1a\u53d1\u751f\u8fd9\u79cd\u60c5\u51b5\u7684\u5730\u65b9).\n",
        "*\n",
        "\u81f3\u4e8e `love is not True or False; love is love`, \u610f\u5916\u5374\u53c8\u4e0d\u8a00\u800c\u55bb.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Yes, it exists!/\u662f\u7684, \u5b83\u5b58\u5728!\n",
        "**\u5faa\u73af\u7684 `else`.** \u4e00\u4e2a\u5178\u578b\u7684\u4f8b\u5b50:\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  def does_exists_num(l, to_find):\n",
        "      for num in l:\n",
        "          if num == to_find:\n",
        "              print(\"Exists!\")\n",
        "              break\n",
        "      else:\n",
        "          print(\"Does not exist\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Exists!\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_list = [1, 2, 3, 4, 5]\n",
        "does_exists_num(some_list, 4)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Does not exist\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "does_exists_num(some_list, -1)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**\u5f02\u5e38\u7684 `else` .** \u4f8b,\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "try:\n",
        "    pass\n",
        "except:\n",
        "    print(\"Exception occurred!!!\")\n",
        "else:\n",
        "    print(\"Try block executed successfully...\")\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Try block executed successfully...\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u5faa\u73af\u540e\u7684 `else` \u5b50\u53e5\u53ea\u4f1a\u5728\u5faa\u73af\u6ca1\u6709\u89e6\u53d1 `break` \u8bed\u53e5, \u6b63\u5e38\u7ed3\u675f\u7684\u60c5\u51b5\u4e0b\u624d\u4f1a\u6267\u884c.\n",
        "- try \u4e4b\u540e\u7684 `else` \u5b50\u53e5\u4e5f\u88ab\u79f0\u4e3a \"\u5b8c\u6210\u5b50\u53e5\", \u56e0\u4e3a\u5728 `try` \u8bed\u53e5\u4e2d\u5230\u8fbe `else` \u5b50\u53e5\u610f\u5473\u7740try\u5757\u5b9e\u9645\u4e0a\u5df2\u6210\u529f\u5b8c\u6210.\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Ellipsis/\u7701\u7565 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def some_func():\n",
        "    Ellipsis\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "# \u6ca1\u6709\u8f93\u51fa\uff0c\u4e5f\u6ca1\u6709\u62a5\u9519\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_func()\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "NameError: name 'SomeRandomString' is not defined\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "SomeRandomString\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Ellipsis\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Ellipsis\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "- \u5728 Python \u4e2d\uff0c`Ellipsis` \u662f\u4e00\u4e2a\u5168\u5c40\u53ef\u7528\u7684\u5185\u7f6e\u5bf9\u8c61\uff0c\u76f8\u5f53\u4e8e`...`\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    Ellipsis\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    ...\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u7701\u7565\u53f7\u53ef\u7528\u4e8e\u591a\u79cd\u7528\u9014\uff0c\n",
        "    + \u4f5c\u4e3a\u5c1a\u672a\u7f16\u5199\u7684\u4ee3\u7801\u7684\u5360\u4f4d\u7b26\uff08\u5c31\u50cf`pass`\u8bed\u53e5\uff09\n",
        "    + \u5728\u5207\u7247\u8bed\u6cd5\u4e2d\u8868\u793a\u5b8c\u6574\u5207\u7247\u7684\u5176\u4f59\u7ef4\u5ea6\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    array([\n",
              "        [\n",
              "            [0, 1],\n",
              "            [2, 3]\n",
              "        ],\n",
              "\n",
              "        [\n",
              "            [4, 5],\n",
              "            [6, 7]\n",
              "        ]\n",
              "    ])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    import numpy as np\n",
        "    three_dimensional_array = np.arange(8).reshape(2, 2, 2)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "    \u6240\u4ee5\u6211\u4eec\u7684 `three_dimensional_array` \u662f\u4e00\u4e2a\u6570\u7ec4\u7684\u6570\u7ec4\u7684\u6570\u7ec4\u3002\u5047\u8bbe\u6211\u4eec\u8981\u6253\u5370\u6240\u6709\u6700\u5185\u5c42\u6570\u7ec4\u7684\u7b2c\u4e8c\u4e2a\u5143\u7d20\uff08\u7d22\u5f15 `1`\uff09\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528 Ellipsis \u7ed5\u8fc7\u6240\u6709\u524d\u9762\u7684\u7ef4\u5ea6\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    array([[1, 3],\n",
              "       [5, 7]])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    three_dimensional_array[:,:,1]\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "    array([[1, 3],\n",
              "       [5, 7]])\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    three_dimensional_array[..., 1] # \u4f7f\u7528Ellipsis.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "    \u6ce8\u610f\uff1a\u8fd9\u9002\u7528\u4e8e\u4efb\u610f\u6570\u91cf\u7684\u7ef4\u5ea6\u3002\u60a8\u751a\u81f3\u53ef\u4ee5\u5728\u7b2c\u4e00\u4e2a\u548c\u6700\u540e\u4e00\u4e2a\u7ef4\u5ea6\u4e2d\u9009\u62e9\u5207\u7247\u5e76\u4ee5\u8fd9\u79cd\u65b9\u5f0f\u5ffd\u7565\u4e2d\u95f4\u7684\u5207\u7247(`n_dimensional_array[firs_dim_slice, ..., last_dim_slice]`)\n",
        "\n",
        "     + \u5728 [\u7c7b\u578b\u63d0\u793a](https://docs.python.org/3/library/typing.html)\u4e2d\u4ec5\u8868\u793a\u7c7b\u578b\u7684\u4e00\u90e8\u5206\uff08\u5982 `(Callable[..., int]` \u6216 `Tuple[ str, ...]`))\n",
        "\n",
        "     + \u60a8\u4e5f\u53ef\u4ee5\u4f7f\u7528\u7701\u7565\u53f7\u4f5c\u4e3a\u9ed8\u8ba4\u51fd\u6570\u53c2\u6570\uff08\u5728\u60a8\u60f3\u8981\u533a\u5206\u201c\u65e0\u53c2\u6570\u201d\u548c\u201c\u4f20\u9012None\u503c\u201d\u573a\u666f\u7684\u60c5\u51b5\u4e0b\uff09\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Inpinity/\u65e0\u9650 *\n",
        "\u82f1\u6587\u62fc\u5199\u662f\u6709\u610f\u7684, \u8bf7\u4e0d\u8981\u4e3a\u6b64\u63d0\u4ea4\u8865\u4e01.\n",
        "(\u8bd1: \u8fd9\u91cc\u662f\u4e3a\u4e86\u7a81\u51fa Python \u4e2d\u65e0\u9650\u7684\u5b9a\u4e49\u4e0e[Pi](https://en.wikipedia.org/wiki/Pi)\u6709\u5173, \u6240\u4ee5\u5c06\u4e24\u4e2a\u5355\u8bcd\u62fc\u63a5\u4e86.)\n",
        "\n",
        "**Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "314159\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "infinity = float('infinity')\n",
        "hash(infinity)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "-314159\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "hash(float('-inf'))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- infinity \u7684\u54c8\u5e0c\u503c\u662f 10\u2075 x \u03c0.\n",
        "- \u6709\u610f\u601d\u7684\u662f, `float('-inf')` \u7684\u54c8\u5e0c\u503c\u5728 Python 3 \u4e2d\u662f \"-10\u2075 x \u03c0\"  , \u800c\u5728 Python 2 \u4e2d\u662f \"-10\u2075 x e\".\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Let's mangle/\u4fee\u9970\u65f6\u95f4! *\n",
        "1\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class Yo(object):\n",
        "    def __init__(self):\n",
        "        self.__honey = True\n",
        "        self.bro = True\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Yo().bro\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "AttributeError: 'Yo' object has no attribute '__honey'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Yo().__honey\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Yo()._Yo__honey\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2\\.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "class Yo(object):\n",
        "    def __init__(self):\n",
        "        # \u8fd9\u6b21\u8bd5\u8bd5\u5bf9\u79f0\u5f62\u5f0f\n",
        "        self.__honey__ = True\n",
        "        self.bro = True\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "True\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Yo().bro\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "AttributeError: 'Yo' object has no attribute '_Yo__honey__'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "Yo()._Yo__honey__\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4e3a\u4ec0\u4e48 `Yo()._Yo__honey` \u80fd\u8fd0\u884c? \u53ea\u6709\u5370\u5ea6\u4eba\u7406\u89e3.(\u8bd1: \u8fd9\u4e2a\u6897\u53ef\u80fd\u662f\u6307\u5370\u5ea6\u97f3\u4e50\u4eba[Yo Yo Honey Singh](https://en.wikipedia.org/wiki/Yo_Yo_Honey_Singh))\n",
        "\n",
        "\n",
        "3\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "_A__variable = \"Some value\"\n",
        "\n",
        "class A(object):\n",
        "    def some_func(self):\n",
        "        return __variable # \u6ca1\u5728\u4efb\u4f55\u5730\u65b9\u521d\u59cb\u5316\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "AttributeError: 'A' object has no attribute '__variable'\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "A().__variable\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "'Some value'\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "A().some_func()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* [\u547d\u540d\u4fee\u9970](https://en.wikipedia.org/wiki/Name_mangling) \u7528\u4e8e\u907f\u514d\u4e0d\u540c\u547d\u540d\u7a7a\u95f4\u4e4b\u95f4\u540d\u79f0\u51b2\u7a81.\n",
        "* \u5728 Python \u4e2d, \u89e3\u91ca\u5668\u4f1a\u901a\u8fc7\u7ed9\u7c7b\u4e2d\u4ee5 `__` (\u53cc\u4e0b\u5212\u7ebf)\u5f00\u5934\u4e14\u7ed3\u5c3e\u6700\u591a\u53ea\u6709\u4e00\u4e2a\u4e0b\u5212\u7ebf\u7684\u7c7b\u6210\u5458\u540d\u79f0\u52a0\u4e0a`_NameOfTheClass` \u6765\u4fee\u9970(mangles)\u540d\u79f0.\n",
        "* \u6240\u4ee5, \u8981\u8bbf\u95ee `__honey` \u5bf9\u8c61,\u6211\u4eec\u9700\u8981\u52a0\u4e0a `_Yo` \u4ee5\u9632\u6b62\u4e0e\u5176\u4ed6\u7c7b\u4e2d\u5b9a\u4e49\u7684\u76f8\u540c\u540d\u79f0\u7684\u5c5e\u6027\u53d1\u751f\u51b2\u7a81.\n",
        "* \u4f46\u662f\u4e3a\u4ec0\u4e48\u5b83\u5728\u7b2c\u4e8c\u4e2a\u7247\u6bb5\u4e2d\u4e0d\u8d77\u4f5c\u7528\uff1f \u56e0\u4e3a\u547d\u540d\u4fee\u9970\u6392\u9664\u4e86\u4ee5\u53cc\u4e0b\u5212\u7ebf\u7ed3\u5c3e\u7684\u540d\u79f0\u3002\n",
        "* \u7b2c\u4e09\u4e2a\u7247\u6bb5\u4e5f\u662f\u547d\u540d\u4fee\u9970\u7684\u7ed3\u679c\u3002 `return __variable` \u8bed\u53e5\u4e2d\u7684 `__variable` \u540d\u79f0\u88ab\u4fee\u6539\u4e3a `_A__variable`\uff0c\u8fd9\u4e5f\u6070\u597d\u662f\u6211\u4eec\u5728\u5916\u90e8\u4f5c\u7528\u57df\u4e2d\u58f0\u660e\u7684\u53d8\u91cf\u7684\u540d\u79f0\u3002\n",
        "* \u6b64\u5916\uff0c\u5982\u679c\u4fee\u9970\u540e\u7684\u53d8\u91cf\u540d\u8d85\u8fc7255\u4e2a\u5b57\u7b26\uff0c\u5219\u4f1a\u8fdb\u884c\u622a\u65ad\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Skipping lines?/\u8df3\u8fc7\u4e00\u884c?\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "11\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "value = 11\n",
        "valu\u0435 = 32\n",
        "value\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4ec0\u4e48\u9b3c?\n",
        "\n",
        "**\u6ce8\u610f:** \u5982\u679c\u4f60\u60f3\u8981\u91cd\u73b0\u7684\u8bdd\u6700\u7b80\u5355\u7684\u65b9\u6cd5\u662f\u76f4\u63a5\u590d\u5236\u4e0a\u9762\u7684\u4ee3\u7801\u7247\u6bb5\u5230\u4f60\u7684\u6587\u4ef6\u6216\u547d\u4ee4\u884c\u91cc.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "\u4e00\u4e9b\u975e\u897f\u65b9\u5b57\u7b26\u867d\u7136\u770b\u8d77\u6765\u548c\u82f1\u8bed\u5b57\u6bcd\u76f8\u540c, \u4f46\u4f1a\u88ab\u89e3\u91ca\u5668\u8bc6\u522b\u4e3a\u4e0d\u540c\u7684\u5b57\u6bcd.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1077\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "ord('\u0435') # \u897f\u91cc\u5c14\u8bed\u7684 'e' (Ye)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "101\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "ord('e') # \u62c9\u4e01\u8bed\u7684 'e', \u7528\u4e8e\u82f1\u6587\u5e76\u4f7f\u7528\u6807\u51c6\u952e\u76d8\u8f93\u5165\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "False\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "'\u0435' == 'e'\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "42\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "value = 42 # \u62c9\u4e01\u8bed e\n",
        "valu\u0435 = 23 # \u897f\u91cc\u5c14\u8bed 'e', Python 2.x \u7684\u89e3\u91ca\u5668\u5728\u8fd9\u4f1a\u629b\u51fa `SyntaxError` \u5f02\u5e38\n",
        "value\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u5185\u7f6e\u7684 `ord()` \u51fd\u6570\u53ef\u4ee5\u8fd4\u56de\u4e00\u4e2a\u5b57\u7b26\u7684 Unicode [\u4ee3\u7801\u70b9](https://en.wikipedia.org/wiki/Code_point), \u8fd9\u91cc\u897f\u91cc\u5c14\u8bed 'e' \u548c\u62c9\u4e01\u8bed 'e' \u7684\u4ee3\u7801\u70b9\u4e0d\u540c\u8bc1\u5b9e\u4e86\u4e0a\u8ff0\u4f8b\u5b50.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Teleportation/\u7a7a\u95f4\u79fb\u52a8 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import numpy as np\n",
        "\n",
        "def energy_send(x):\n",
        "    # \u521d\u59cb\u5316\u4e00\u4e2a numpy \u6570\u7ec4\n",
        "    np.array([float(x)])\n",
        "\n",
        "def energy_receive():\n",
        "    # \u8fd4\u56de\u4e00\u4e2a\u7a7a\u7684 numpy \u6570\u7ec4\n",
        "    return np.empty((), dtype=np.float).tolist()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "123.456\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "energy_send(123.456)\n",
        "energy_receive()\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8c01\u6765\u7ed9\u6211\u53d1\u4e2a\u8bfa\u8d1d\u5c14\u5956?\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* \u6ce8\u610f\u5728 `energy_send` \u51fd\u6570\u4e2d\u521b\u5efa\u7684 numpy \u6570\u7ec4\u5e76\u6ca1\u6709\u8fd4\u56de, \u56e0\u6b64\u5185\u5b58\u7a7a\u95f4\u88ab\u91ca\u653e\u5e76\u53ef\u4ee5\u88ab\u91cd\u65b0\u5206\u914d.\n",
        "* `numpy.empty()` \u76f4\u63a5\u8fd4\u56de\u4e0b\u4e00\u6bb5\u7a7a\u95f2\u5185\u5b58\uff0c\u800c\u4e0d\u91cd\u65b0\u521d\u59cb\u5316. \u800c\u8fd9\u4e2a\u5185\u5b58\u70b9\u6070\u597d\u5c31\u662f\u521a\u521a\u91ca\u653e\u7684\u90a3\u4e2a(\u901a\u5e38\u60c5\u51b5\u4e0b, \u5e76\u4e0d\u7edd\u5bf9).\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Well, something is fishy.../\u55ef\uff0c\u6709\u4e9b\u53ef\u7591...\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def square(x):\n",
        "    \"\"\"\n",
        "    \u4e00\u4e2a\u901a\u8fc7\u52a0\u6cd5\u8ba1\u7b97\u5e73\u65b9\u7684\u7b80\u5355\u51fd\u6570.\n",
        "    \"\"\"\n",
        "    sum_so_far = 0\n",
        "    for counter in range(x):\n",
        "        sum_so_far = sum_so_far + x\n",
        "  return sum_so_far\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output (Python 2.x):**\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "10\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "square(10)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u96be\u9053\u4e0d\u5e94\u8be5\u662f100\u5417?\n",
        "\n",
        "**\u6ce8\u610f:** \u5982\u679c\u4f60\u65e0\u6cd5\u91cd\u73b0, \u53ef\u4ee5\u5c1d\u8bd5\u8fd0\u884c\u8fd9\u4e2a\u6587\u4ef6[mixed_tabs_and_spaces.py](/mixed_tabs_and_spaces.py).\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "\n",
        "* **\u4e0d\u8981\u6df7\u7528\u5236\u8868\u7b26(tab)\u548c\u7a7a\u683c(space)!** \u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d, return \u7684\u524d\u9762\u662f\"1\u4e2a\u5236\u8868\u7b26\", \u800c\u5176\u4ed6\u90e8\u5206\u7684\u4ee3\u7801\u524d\u9762\u662f \"4\u4e2a\u7a7a\u683c\".\n",
        "* Python\u662f\u8fd9\u4e48\u5904\u7406\u5236\u8868\u7b26\u7684:\n",
        "  > \u9996\u5148, \u5236\u8868\u7b26\u4f1a\u4ece\u5de6\u5230\u53f3\u4f9d\u6b21\u88ab\u66ff\u6362\u62108\u4e2a\u7a7a\u683c, \u76f4\u5230\u88ab\u66ff\u6362\u540e\u7684\u5b57\u7b26\u603b\u6570\u662f\u516b\u7684\u500d\u6570 <...>\n",
        "* \u56e0\u6b64, `square` \u51fd\u6570\u6700\u540e\u4e00\u884c\u7684\u5236\u8868\u7b26\u4f1a\u88ab\u66ff\u6362\u62108\u4e2a\u7a7a\u683c, \u5bfc\u81f4return\u8bed\u53e5\u8fdb\u5165\u5faa\u73af\u8bed\u53e5\u91cc\u9762.\n",
        "* Python 3 \u5f88\u53cb\u597d, \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u4f1a\u81ea\u52a8\u629b\u51fa\u9519\u8bef.\n",
        "\n",
        "    **Output (Python 3.x):**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "    TabError: inconsistent use of tabs and spaces in indentation\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > `+=` is faster/\u66f4\u5feb\u7684 `+=`\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0.25748300552368164\n",
              "# \u7528 \"+=\" \u8fde\u63a5\u4e09\u4e2a\u5b57\u7b26\u4e32:\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "# \u7528 \"+\" \u8fde\u63a5\u4e09\u4e2a\u5b57\u7b26\u4e32:\n",
        "timeit.timeit(\"s1 = s1 + s2 + s3\", setup=\"s1 = ' ' * 100000; s2 = ' ' * 100000; s3 = ' ' * 100000\", number=100)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "0.012188911437988281\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit.timeit(\"s1 += s2 + s3\", setup=\"s1 = ' ' * 100000; s2 = ' ' * 100000; s3 = ' ' * 100000\", number=100)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "+ \u8fde\u63a5\u4e24\u4e2a\u4ee5\u4e0a\u7684\u5b57\u7b26\u4e32\u65f6 `+=` \u6bd4 `+` \u66f4\u5feb, \u56e0\u4e3a\u5728\u8ba1\u7b97\u8fc7\u7a0b\u4e2d\u7b2c\u4e00\u4e2a\u5b57\u7b26\u4e32 (\u4f8b\u5982, `s1 += s2 + s3` \u4e2d\u7684 `s1`) \u4e0d\u4f1a\u88ab\u9500\u6bc1.(\u8bd1: \u5c31\u662f `+=` \u6267\u884c\u7684\u662f\u8ffd\u52a0\u64cd\u4f5c\uff0c\u5c11\u4e86\u4e00\u4e2a\u9500\u6bc1\u65b0\u5efa\u7684\u52a8\u4f5c.)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Let's make a giant string!/\u6765\u505a\u4e2a\u5de8\u5927\u7684\u5b57\u7b26\u4e32\u5427\uff01\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "def add_string_with_plus(iters):\n",
        "    s = \"\"\n",
        "    for i in range(iters):\n",
        "        s += \"xyz\"\n",
        "    assert len(s) == 3*iters\n",
        "\n",
        "def add_bytes_with_plus(iters):\n",
        "    s = b\"\"\n",
        "    for i in range(iters):\n",
        "        s += b\"xyz\"\n",
        "    assert len(s) == 3*iters\n",
        "\n",
        "def add_string_with_format(iters):\n",
        "    fs = \"{}\"*iters\n",
        "    s = fs.format(*([\"xyz\"]*iters))\n",
        "    assert len(s) == 3*iters\n",
        "\n",
        "def add_string_with_join(iters):\n",
        "    l = []\n",
        "    for i in range(iters):\n",
        "        l.append(\"xyz\")\n",
        "    s = \"\".join(l)\n",
        "    assert len(s) == 3*iters\n",
        "\n",
        "def convert_list_to_string(l, iters):\n",
        "    s = \"\".join(l)\n",
        "    assert len(s) == 3*iters\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 972 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_plus(10000))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 815 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_bytes_with_plus(10000))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 508 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_format(10000))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 878 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_join(10000))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "10000 loops, best of 3: 80 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "l = [\"xyz\"]*10000\n",
        "timeit(convert_list_to_string(l, 10000))\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8ba9\u6211\u4eec\u5c06\u8fed\u4ee3\u6b21\u6570\u589e\u52a010\u500d.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "100 loops, best of 3: 9.75 ms per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_plus(100000)) # \u6267\u884c\u65f6\u95f4\u7ebf\u6027\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 974 ms per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_bytes_with_plus(100000)) # \u4e8c\u6b21\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "100 loops, best of 3: 5.25 ms per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_format(100000)) # \u7ebf\u6027\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "100 loops, best of 3: 9.85 ms per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "timeit(add_string_with_join(100000)) # \u7ebf\u6027\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "1000 loops, best of 3: 723 \u00b5s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "l = [\"xyz\"]*100000\n",
        "timeit(convert_list_to_string(l, 100000)) # \u7ebf\u6027\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e:\n",
        "- \u4f60\u53ef\u4ee5\u5728\u8fd9\u83b7\u5f97\u66f4\u591a [timeit](https://docs.python.org/3/library/timeit.html) \u7684\u76f8\u5173\u4fe1\u606f. \u5b83\u901a\u5e38\u7528\u4e8e\u8861\u91cf\u4ee3\u7801\u7247\u6bb5\u7684\u6267\u884c\u65f6\u95f4.\n",
        "- \u4e0d\u8981\u7528 `+` \u53bb\u751f\u6210\u8fc7\u957f\u7684\u5b57\u7b26\u4e32, \u5728 Python \u4e2d, `str` \u662f\u4e0d\u53ef\u53d8\u7684, \u6240\u4ee5\u5728\u6bcf\u6b21\u8fde\u63a5\u4e2d\u4f60\u90fd\u8981\u628a\u5de6\u53f3\u4e24\u4e2a\u5b57\u7b26\u4e32\u590d\u5236\u5230\u65b0\u7684\u5b57\u7b26\u4e32\u4e2d. \u5982\u679c\u4f60\u8fde\u63a5\u56db\u4e2a\u957f\u5ea6\u4e3a10\u7684\u5b57\u7b26\u4e32, \u4f60\u9700\u8981\u62f7\u8d1d (10+10) + ((10+10)+10) + (((10+10)+10)+10) = 90 \u4e2a\u5b57\u7b26\u800c\u4e0d\u662f 40 \u4e2a\u5b57\u7b26. \u968f\u7740\u5b57\u7b26\u4e32\u7684\u6570\u91cf\u548c\u5927\u5c0f\u7684\u589e\u52a0, \u60c5\u51b5\u4f1a\u53d8\u5f97\u8d8a\u53d1\u7684\u7cdf\u7cd5 (\u5c31\u50cf`add_bytes_with_plus` \u51fd\u6570\u7684\u6267\u884c\u65f6\u95f4\u4e00\u6837)\n",
        "- \u56e0\u6b64, \u66f4\u5efa\u8bae\u4f7f\u7528 `.format.` \u6216 `%` \u8bed\u6cd5 (\u4f46\u662f, \u5bf9\u4e8e\u77ed\u5b57\u7b26\u4e32, \u5b83\u4eec\u6bd4 `+` \u7a0d\u6162\u4e00\u70b9).\n",
        "- \u53c8\u6216\u8005, \u5982\u679c\u4f60\u6240\u9700\u7684\u5185\u5bb9\u5df2\u7ecf\u4ee5\u53ef\u8fed\u4ee3\u5bf9\u8c61\u7684\u5f62\u5f0f\u63d0\u4f9b\u4e86, \u4f7f\u7528 `''.join(\u53ef\u8fed\u4ee3\u5bf9\u8c61)` \u8981\u5feb\u591a\u4e86.\n",
        "- `add_string_with_plus` \u7684\u6267\u884c\u65f6\u95f4\u6ca1\u6709\u50cf `add_bytes_with_plus` \u4e00\u6837\u51fa\u73b0\u4e8c\u6b21\u589e\u52a0\u662f\u56e0\u4e3a\u89e3\u91ca\u5668\u4f1a\u5982\u540c\u4e0a\u4e00\u4e2a\u4f8b\u5b50\u6240\u8ba8\u8bba\u7684\u4e00\u6837\u4f18\u5316 `+=`. \u7528 `s = s + \"x\" + \"y\" + \"z\"` \u66ff\u4ee3 `s += \"xyz\"` \u7684\u8bdd, \u6267\u884c\u65f6\u95f4\u5c31\u4f1a\u4e8c\u6b21\u589e\u52a0\u4e86.\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  100 loops, best of 3: 9.87 ms per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  def add_string_with_plus(iters):\n",
        "      s = \"\"\n",
        "      for i in range(iters):\n",
        "          s = s + \"x\" + \"y\" + \"z\"\n",
        "      assert len(s) == 3*iters\n",
        "\n",
        "  timeit(add_string_with_plus(10000))\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "  1 loops, best of 3: 1.09 s per loop\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "  timeit(add_string_with_plus(100000)) # \u6267\u884c\u65f6\u95f4\u4e8c\u6b21\u589e\u52a0\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Slowing down `dict` lookups/\u8ba9\u5b57\u5178\u7684\u67e5\u627e\u6162\u4e0b\u6765 *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict = {str(i): 1 for i in range(1_000_000)}\n",
        "another_dict = {str(i): 1 for i in range(1_000_000)}\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:**\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "28.6 ns \u00b1 0.115 ns per loop (mean \u00b1 std. dev. of 7 runs, 10000000 loops each)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "%timeit some_dict['5']\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "37.2 ns \u00b1 0.265 ns per loop (mean \u00b1 std. dev. of 7 runs, 10000000 loops each)\n",
              "\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "some_dict[1] = 1\n",
        "%timeit some_dict['5']\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "28.5 ns \u00b1 0.142 ns per loop (mean \u00b1 std. dev. of 7 runs, 10000000 loops each)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "%timeit another_dict['5']\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "Traceback (most recent call last):\n",
              "  File \"<stdin>\", line 1, in <module>\n",
              "KeyError: 1\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "another_dict[1]  # Trying to access a key that doesn't exist\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "38.5 ns \u00b1 0.0913 ns per loop (mean \u00b1 std. dev. of 7 runs, 10000000 loops each)\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "%timeit another_dict['5']\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u4e3a\u4ec0\u4e48\u76f8\u540c\u7684\u67e5\u627e\u4f1a\u53d8\u5f97\u8d8a\u6765\u8d8a\u6162\uff1f\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "+ CPython \u6709\u4e00\u4e2a\u901a\u7528\u7684\u5b57\u5178\u67e5\u627e\u51fd\u6570\uff0c\u53ef\u4ee5\u5904\u7406\u6240\u6709\u7c7b\u578b\u7684\u952e\uff08`str`\u3001`int`\u3001\u4efb\u4f55\u5bf9\u8c61...\uff09\uff0c\u4ee5\u53ca\u4e00\u4e2a\u4e13\u95e8\u7528\u4e8e\u5904\u7406\u4ec5\u7531 `str` \u952e\u7ec4\u6210\u7684\u5b57\u5178\u7684\u5e38\u89c1\u60c5\u51b5\u3002\n",
        "+ \u4e13\u7528\u51fd\u6570\uff08\u5728 CPython \u7684 [\u6e90](https://github.com/python/cpython/blob/522691c46e2ae51faaad5bbbce7d959dd61770df/Objects/dictobject.c#L841) \u4e2d\u540d\u4e3a `lookdict_unicode`\uff09\u77e5\u9053\u6240\u6709\u73b0\u6709\u7684\u952e\uff08\u5305\u62ec\u67e5\u627e\u7684 key) \u662f\u5b57\u7b26\u4e32\uff0c\u5e76\u4f7f\u7528\u66f4\u5feb\u548c\u66f4\u7b80\u5355\u7684\u5b57\u7b26\u4e32\u6bd4\u8f83\u6765\u6bd4\u8f83\u952e\uff0c\u800c\u4e0d\u662f\u8c03\u7528 `__eq__` \u65b9\u6cd5\u3002\n",
        "+ \u7b2c\u4e00\u6b21\u4f7f\u7528\u975e `str` \u952e\u8bbf\u95ee `dict` \u5b9e\u4f8b\u65f6\uff0c\u4f1a\u5bf9\u5176\u8fdb\u884c\u4fee\u6539\uff0c\u4ee5\u4fbf\u5c06\u6765\u7684\u67e5\u627e\u4f7f\u7528\u901a\u7528\u51fd\u6570\u3002\n",
        "+ \u8fd9\u4e2a\u8fc7\u7a0b\u5bf9\u4e8e\u7279\u5b9a\u7684 `dict` \u5b9e\u4f8b\u662f\u4e0d\u53ef\u9006\u7684\uff0c\u5e76\u4e14\u952e\u751a\u81f3\u4e0d\u5fc5\u5b58\u5728\u4e8e\u5b57\u5178\u4e2d\u3002 \u8fd9\u5c31\u662f\u4e3a\u4ec0\u4e48\u5bf9\u4e0d\u5b58\u5728\u7684\u952e\u8fdb\u884c\u67e5\u627e\u5177\u6709\u76f8\u540c\u526f\u4f5c\u7528\u7684\u539f\u56e0\u3002\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Bloating instance `dict`s/\u53d8\u81c3\u80bf\u7684`dict`\u5b9e\u4f8b\u4eec *\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": []
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "import sys\n",
        "\n",
        "class SomeClass:\n",
        "    def __init__(self):\n",
        "        self.some_attr1 = 1\n",
        "        self.some_attr2 = 2\n",
        "        self.some_attr3 = 3\n",
        "        self.some_attr4 = 4\n",
        "\n",
        "\n",
        "def dict_size(o):\n",
        "    return sys.getsizeof(o.__dict__)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output:** (Python 3.8, \u5176\u4ed6 Python 3 \u7684\u7248\u672c\u4e5f\u8bb8\u7a0d\u6709\u4e0d\u540c)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "104\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1 = SomeClass()\n",
        "o2 = SomeClass()\n",
        "dict_size(o1)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "104\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dict_size(o2)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "232\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "del o1.some_attr1\n",
        "o3 = SomeClass()\n",
        "dict_size(o3)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "232\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dict_size(o1)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u8ba9\u6211\u4eec\u5728\u4e00\u4e2a\u65b0\u7684\u89e3\u91ca\u5668\u4e2d\u518d\u8bd5\u4e00\u6b21\uff1a\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "104  # \u610f\u6599\u4e4b\u4e2d\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1 = SomeClass()\n",
        "o2 = SomeClass()\n",
        "dict_size(o1)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "360\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o1.some_attr5 = 5\n",
        "o1.some_attr6 = 6\n",
        "dict_size(o1)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "272\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "dict_size(o2)\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": true
      },
      "outputs": [
        {
          "data": {
            "text/plain": [
              "232\n"
            ]
          },
          "output_type": "execute_result",
          "metadata": {},
          "execution_count": null
        }
      ],
      "source": [
        "o3 = SomeClass()\n",
        "dict_size(o3)\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\u662f\u4ec0\u4e48\u8ba9\u90a3\u4e9b\u5b57\u5178\u53d8\u5f97\u81c3\u80bf\uff1f \u4e3a\u4ec0\u4e48\u65b0\u521b\u5efa\u7684\u5bf9\u8c61\u4e5f\u4f1a\u53d8\u81c3\u80bf\uff1f\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "+ CPython \u80fd\u591f\u5728\u591a\u4e2a\u5b57\u5178\u4e2d\u91cd\u7528\u76f8\u540c\u7684\u201c\u952e\u201d\u5bf9\u8c61\u3002 \u8fd9\u6dfb\u52a0\u5728 [PEP 412](https://www.python.org/dev/peps/pep-0412/) \u4e2d\uff0c\u76ee\u7684\u662f\u51cf\u5c11\u5185\u5b58\u4f7f\u7528\uff0c\u7279\u522b\u662f\u5728\u5b9e\u4f8b\u5b57\u5178\u4e2d \u2014\u2014 \u952e\uff08\u5b9e\u4f8b\u5c5e\u6027\uff09\u51e0\u4e4e\u5728\u6240\u6709\u5b9e\u4f8b\u90fd\u901a\u7528\u3002\n",
        "+ \u8fd9\u79cd\u4f18\u5316\u5bf9\u4e8e\u5b9e\u4f8b\u5b57\u5178\u6765\u8bf4\u662f\u5341\u5206\u81ea\u7136\u7684\uff0c\u4f46\u5982\u679c\u67d0\u4e9b\u5047\u8bbe\u88ab\u6253\u7834\uff0c\u5b83\u5c31\u4f1a\u88ab\u7981\u7528\u3002\n",
        "+ \u5bc6\u94a5\u5171\u4eab\u5b57\u5178\u4e0d\u652f\u6301\u5220\u9664\uff1b\u5982\u679c\u5220\u9664\u4e86\u5b9e\u4f8b\u5c5e\u6027\uff0c\u5219\u5b57\u5178\u662f\u201c\u672a\u5171\u4eab\u7684\u201d\uff0c\u5e76\u4e14\u540c\u4e00\u7c7b\u7684\u6240\u6709\u672a\u6765\u5b9e\u4f8b\u90fd\u7981\u7528\u5bc6\u94a5\u5171\u4eab\u3002\n",
        "+ \u53e6\u5916\uff0c\u5982\u679c\u5b57\u5178\u952e\u5df2\u88ab\u8c03\u6574\u5927\u5c0f\uff08\u56e0\u4e3a\u63d2\u5165\u4e86\u65b0\u952e\uff09\uff0c\u5b83\u4eec\u4fdd\u6301\u5171\u4eab*\u4ec5\u5f53*\u5b83\u4eec\u88ab\u4e00\u4e2a\u5b8c\u5168\u5355\u4e00\u7684\u5b57\u5178\u4f7f\u7528\u65f6\uff08\u8fd9\u5141\u8bb8\u5728\u7b2c\u4e00\u4e2a\u521b\u5efa\u7684\u5b9e\u4f8b\u7684 `__init__` \u4e2d\u6dfb\u52a0\u8bb8\u591a\u5c5e\u6027\uff0c\u800c\u4e0d\u4f1a\u5bfc\u81f4\u201c\u53d6\u6d88\u5171\u4eab\u201d\uff09\u3002\u5982\u679c\u53d1\u751f\u8c03\u6574\u5927\u5c0f\u65f6\u5b58\u5728\u591a\u4e2a\u5b9e\u4f8b\uff0c\u5219\u4e3a\u540c\u4e00\u7c7b\u7684\u6240\u6709\u672a\u6765\u5b9e\u4f8b\u7981\u7528\u5bc6\u94a5\u5171\u4eab\uff1aCPython \u65e0\u6cd5\u5224\u65ad\u60a8\u7684\u5b9e\u4f8b\u662f\u5426\u6b63\u5728\u4f7f\u7528\u76f8\u540c\u7684\u5c5e\u6027\u96c6\uff0c\u5e76\u51b3\u5b9a\u653e\u5f03\u5c1d\u8bd5\u5171\u4eab\u5b83\u4eec\u7684\u952e\u503c\u3002\n",
        "+ \u4e00\u4e2a\u5c0f\u63d0\u793a\uff0c\u5982\u679c\u4f60\u7684\u76ee\u6807\u662f\u964d\u4f4e\u7a0b\u5e8f\u7684\u5185\u5b58\u5360\u7528\uff1a\u4e0d\u8981\u5220\u9664\u5b9e\u4f8b\u5c5e\u6027\uff0c\u5e76\u786e\u4fdd\u5728 `__init__` \u4e2d\u521d\u59cb\u5316\u6240\u6709\u7684\u5c5e\u6027\uff01\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Minor Ones/\u5c0f\u77e5\u8bc6\u70b9\n",
        "* `join()` \u662f\u4e00\u4e2a\u5b57\u7b26\u4e32\u64cd\u4f5c\u800c\u4e0d\u662f\u5217\u8868\u64cd\u4f5c. (\u7b2c\u4e00\u6b21\u63a5\u89e6\u4f1a\u89c9\u5f97\u6709\u70b9\u8fdd\u53cd\u76f4\u89c9)\n",
        "\n",
        "  **\ud83d\udca1 \u8bf4\u660e:**\n",
        "  \u5982\u679c `join()` \u662f\u5b57\u7b26\u4e32\u65b9\u6cd5 \u90a3\u4e48\u5b83\u5c31\u53ef\u4ee5\u5904\u7406\u4efb\u4f55\u53ef\u8fed\u4ee3\u7684\u5bf9\u8c61(\u5217\u8868\uff0c\u5143\u7ec4\uff0c\u8fed\u4ee3\u5668). \u5982\u679c\u5b83\u662f\u5217\u8868\u65b9\u6cd5, \u5219\u5fc5\u987b\u5728\u6bcf\u79cd\u7c7b\u578b\u4e2d\u5355\u72ec\u5b9e\u73b0. \u53e6\u5916, \u5728 `list` \u5bf9\u8c61\u7684\u901a\u7528API\u4e2d\u5b9e\u73b0\u4e00\u4e2a\u4e13\u7528\u4e8e\u5b57\u7b26\u4e32\u7684\u65b9\u6cd5\u6ca1\u6709\u592a\u5927\u7684\u610f\u4e49.\n",
        "\n",
        "* \u770b\u7740\u5947\u602a\u4f46\u80fd\u6b63\u786e\u8fd0\u884c\u7684\u8bed\u53e5:\n",
        "  + `[] = ()` \u8bed\u53e5\u5728\u8bed\u4e49\u4e0a\u662f\u6b63\u786e\u7684 (\u89e3\u5305\u4e00\u4e2a\u7a7a\u7684 `tuple` \u5e76\u8d4b\u503c\u7ed9 `list`)\n",
        "  + `'a'[0][0][0][0][0]` \u5728\u8bed\u4e49\u4e0a\u4e5f\u662f\u6b63\u786e\u7684, \u56e0\u4e3a\u5728 Python \u4e2d\u5b57\u7b26\u4e32\u540c\u65f6\u4e5f\u662f[\u5e8f\u5217](https://docs.python.org/3/glossary.html#term-sequence)(\u53ef\u8fed\u4ee3\u5bf9\u8c61\u652f\u6301\u4f7f\u7528\u6574\u6570\u7d22\u5f15\u8bbf\u95ee\u5143\u7d20).\n",
        "  + `3 --0-- 5 == 8` \u548c `--5 == 5` \u5728\u8bed\u4e49\u4e0a\u90fd\u662f\u6b63\u786e\u7684, \u4e14\u7ed3\u679c\u7b49\u4e8e `True`.(\u8bd1: 3\u51cf\u8d1f0\u7b49\u4e8e3\uff0c\u518d\u51cf\u8d1f5\u76f8\u5f53\u4e8e\u52a05\u7b49\u4e8e8\uff1b\u8d1f\u7684\u8d1f5\u7b49\u4e8e5.)\n",
        "\n",
        "* \u9274\u4e8e `a` \u662f\u4e00\u4e2a\u6570\u5b57, `++a` \u548c `--a` \u90fd\u662f\u6709\u6548\u7684 Python \u8bed\u53e5, \u4f46\u5176\u6548\u679c\u4e0e C, C++ \u6216 Java \u7b49\u4e0d\u4e00\u6837.\n",
        "  ```py\n",
        "  >>> a = 5\n",
        "  >>> a\n",
        "  5\n",
        "  >>> ++a\n",
        "  5\n",
        "  >>> --a\n",
        "  5\n",
        "  ```\n",
        "\n",
        "  **\ud83d\udca1 \u8bf4\u660e:**\n",
        "  + python \u91cc\u6ca1\u6709 `++` \u64cd\u4f5c\u7b26. \u8fd9\u5176\u5b9e\u662f\u4e24\u4e2a `+` \u64cd\u4f5c\u7b26.\n",
        "  + `++a` \u88ab\u89e3\u6790\u4e3a `+(+a)` \u6700\u540e\u7b49\u4e8e `a`. `--a` \u540c\u7406.\n",
        "  + \u8fd9\u4e2a StackOverflow [\u56de\u7b54](https://stackoverflow.com/questions/3654830/why-are-there-no-and-operators-in-python) \u8ba8\u8bba\u4e86\u4e3a\u4ec0\u4e48 Python \u4e2d\u7f3a\u5c11\u589e\u91cf\u548c\u51cf\u91cf\u8fd0\u7b97\u7b26.\n",
        "\n",
        "* Python \u4f7f\u7528 2\u4e2a\u5b57\u8282\u5b58\u50a8\u51fd\u6570\u4e2d\u7684\u672c\u5730\u53d8\u91cf. \u7406\u8bba\u4e0a, \u8fd9\u610f\u5473\u7740\u51fd\u6570\u4e2d\u53ea\u80fd\u5b9a\u4e4965536\u4e2a\u53d8\u91cf. \u4f46\u662f\uff0cPython \u5185\u7f6e\u4e86\u4e00\u4e2a\u65b9\u4fbf\u7684\u89e3\u51b3\u65b9\u6848\uff0c\u53ef\u7528\u4e8e\u5b58\u50a8\u8d85\u8fc72^16\u4e2a\u53d8\u91cf\u540d. \u4e0b\u9762\u7684\u4ee3\u7801\u6f14\u793a\u4e86\u5f53\u5b9a\u4e49\u4e86\u8d85\u8fc765536\u4e2a\u5c40\u90e8\u53d8\u91cf\u65f6\u5806\u6808\u4e2d\u53d1\u751f\u7684\u60c5\u51b5 (\u8b66\u544a: \u8fd9\u6bb5\u4ee3\u7801\u4f1a\u6253\u5370\u5927\u7ea62^18\u884c\u6587\u672c, \u8bf7\u505a\u597d\u51c6\u5907!):\n",
        "     ```py\n",
        "     import dis\n",
        "     exec(\"\"\"\n",
        "     def f():\n",
        "         \"\"\" + \"\"\"\n",
        "         \"\"\".join([\"X\"+str(x)+\"=\" + str(x) for x in range(65539)]))\n",
        "\n",
        "     f()\n",
        "\n",
        "     print(dis.dis(f))\n",
        "     ```\n",
        "\n",
        "* \u4f60\u7684 *Python \u4ee3\u7801* \u5e76\u4e0d\u4f1a\u591a\u7ebf\u7a0b\u540c\u65f6\u8fd0\u884c (\u662f\u7684, \u4f60\u6ca1\u542c\u9519!). \u867d\u7136\u4f60\u89c9\u5f97\u4f1a\u4ea7\u751f\u591a\u4e2a\u7ebf\u7a0b\u5e76\u8ba9\u5b83\u4eec\u540c\u65f6\u6267\u884c\u4f60\u7684\u4ee3\u7801, \u4f46\u662f, \u7531\u4e8e [\u5168\u5c40\u89e3\u91ca\u9501](https://wiki.python.org/moin/GlobalInterpreterLock)\u7684\u5b58\u5728, \u4f60\u6240\u505a\u7684\u53ea\u662f\u8ba9\u4f60\u7684\u7ebf\u7a0b\u4f9d\u6b21\u5728\u540c\u4e00\u4e2a\u6838\u5fc3\u4e0a\u6267\u884c. Python \u591a\u7ebf\u7a0b\u9002\u7528\u4e8eIO\u5bc6\u96c6\u578b\u7684\u4efb\u52a1, \u4f46\u5982\u679c\u60f3\u8981\u5e76\u884c\u5904\u7406CPU\u5bc6\u96c6\u578b\u7684\u4efb\u52a1, \u4f60\u5e94\u8be5\u4f1a\u60f3\u4f7f\u7528 [multiprocessing](https://docs.python.org/2/library/multiprocessing.html) \u6a21\u5757.\n",
        "\n",
        "* \u5217\u8868\u5207\u7247\u8d85\u51fa\u7d22\u5f15\u8fb9\u754c\u800c\u4e0d\u5f15\u53d1\u4efb\u4f55\u9519\u8bef\n",
        "  ```py\n",
        "  >>> some_list = [1, 2, 3, 4, 5]\n",
        "  >>> some_list[111:]\n",
        "  []\n",
        "  ```\n",
        "\n",
        "* `int('\u0661\u0662\u0663\u0664\u0665\u0666\u0667\u0668\u0669')` \u5728 Python 3 \u4e2d\u4f1a\u8fd4\u56de `123456789`. \u5728 Python \u4e2d, \u5341\u8fdb\u5236\u5b57\u7b26\u5305\u62ec\u6570\u5b57\u5b57\u7b26, \u4ee5\u53ca\u53ef\u7528\u4e8e\u5f62\u6210\u5341\u8fdb\u5236\u6570\u5b57\u7684\u6240\u6709\u5b57\u7b26, \u4f8b\u5982: U+0660, ARABIC-INDIC DIGIT ZERO. \u8fd9\u6709\u4e00\u4e2a\u5173\u4e8e\u6b64\u7684 [\u6709\u8da3\u6545\u4e8b](http://chris.improbable.org/2014/8/25/adventures-in-unicode-digits/).\n",
        "\n",
        "* `'abc'.count('') == 4`. \u8fd9\u6709\u4e00\u4e2a `count` \u65b9\u6cd5\u7684\u76f8\u8fd1\u5b9e\u73b0, \u80fd\u66f4\u597d\u7684\u8bf4\u660e\u95ee\u9898\n",
        "  ```py\n",
        "  def count(s, sub):\n",
        "      result = 0\n",
        "      for i in range(len(s) + 1 - len(sub)):\n",
        "          result += (s[i:i + len(sub)] == sub)\n",
        "      return result\n",
        "  ```\n",
        "  \u8fd9\u4e2a\u884c\u4e3a\u662f\u7531\u4e8e\u7a7a\u5b50\u4e32(`''`)\u4e0e\u539f\u59cb\u5b57\u7b26\u4e32\u4e2d\u957f\u5ea6\u4e3a0\u7684\u5207\u7247\u76f8\u5339\u914d\u5bfc\u81f4\u7684.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > First things first!/\u8981\u4e8b\u4f18\u5148 *\n",
        "\u4f17\u6240\u5468\u77e5\uff0cPython 3.8 \u63a8\u51fa\"\u6d77\u8c61\"\u8fd0\u7b97\u7b26 (`:=`) \u65b9\u4fbf\u6613\u7528\uff0c\u8ba9\u6211\u4eec\u4e00\u8d77\u770b\u770b\u3002\n",
        "\n",
        "1\\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "# Python \u7248\u672c 3.8+\n",
        "\n",
        ">>> a = \"wtf_walrus\"\n",
        ">>> a\n",
        "```\n",
        "```py\n",
        "'wtf_walrus'\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> a := \"wtf_walrus\"\n",
        "```\n",
        "```py\n",
        "File \"<stdin>\", line 1\n",
        "    a := \"wtf_walrus\"\n",
        "      ^\n",
        "SyntaxError: invalid syntax\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> (a := \"wtf_walrus\") # \u8be5\u8bed\u53e5\u6709\u6548\n",
        "```\n",
        "```py\n",
        "'wtf_walrus'\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> a\n",
        "```\n",
        "```py\n",
        "'wtf_walrus'\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "2 \\.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "# Python \u7248\u672c 3.8+\n",
        "\n",
        ">>> a = 6, 9\n",
        ">>> a\n",
        "```\n",
        "```py\n",
        "(6, 9)\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> (a := 6, 9)\n",
        "```\n",
        "```py\n",
        "(6, 9)\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> a\n",
        "```\n",
        "```py\n",
        "6\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> a, b = 6, 9 # \u5178\u578b\u62c6\u5305\u64cd\u4f5c\n",
        ">>> a, b\n",
        "```\n",
        "```py\n",
        "(6, 9)\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> (a, b = 16, 19) # \u51fa\u9519\u5566\n",
        "```\n",
        "```py\n",
        "  File \"<stdin>\", line 1\n",
        "    (a, b = 16, 19)\n",
        "          ^\n",
        "SyntaxError: invalid syntax\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> (a, b := 16, 19) # \u8fd9\u91cc\u7684\u7ed3\u679c\u662f\u4e00\u4e2a\u5947\u602a\u7684\u4e09\u5143\u7ec4\n",
        "```\n",
        "```py\n",
        "(6, 16, 19)\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> a # a\u503c\u4ecd\u7136\u6ca1\u53d8?\n",
        "```\n",
        "```py\n",
        "6\n",
        "\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> b\n",
        "```\n",
        "```py\n",
        "16\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "**\u201c\u6d77\u8c61\u201d\u8fd0\u7b97\u7b26\u7b80\u4ecb**\n",
        "\n",
        "\u6d77\u8c61\u8fd0\u7b97\u7b26 (`:=`) \u5728Python 3.8\u4e2d\u88ab\u5f15\u5165\uff0c\u7528\u6765\u5728\u8868\u8fbe\u5f0f\u4e2d\u4e3a\u53d8\u91cf\u8d4b\u503c\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "def some_func():\n",
        "        # \u5047\u8bbe\u8fd9\u513f\u6709\u4e00\u4e9b\u8017\u65f6\u7684\u8ba1\u7b97\n",
        "        # time.sleep(1000)\n",
        "        return 5\n",
        "\n",
        "# \u5f15\u5165\u201c\u6d77\u8c61\u201d\u8fd0\u7b97\u7b26\u524d\u7684\u4f8b\u5b50\n",
        "if some_func():\n",
        "        print(some_func()) # \u7cdf\u7cd5\u7684\u6848\u4f8b\u2014\u2014\u51fd\u6570\u8fd0\u7b97\u4e86\u4e24\u6b21\n",
        "\n",
        "# \u6216\u8005\uff0c\u52a0\u4ee5\u6539\u8fdb\uff1a\n",
        "a = some_func()\n",
        "if a:\n",
        "    print(a)\n",
        "\n",
        "# \u6709\u4e86\u201c\u6d77\u8c61\u201d\u8fd0\u7b97\u7b26\uff0c\u4f60\u53ef\u4ee5\u5199\u7684\u66f4\u7b80\u6d01\uff1a\n",
        "if a := some_func():\n",
        "        print(a)\n",
        "```\n",
        "```py\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**\u8f93\u51fa (> Python 3.8):**\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "5\n",
        "5\n",
        "5\n",
        "```\n",
        "```py\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\u8fd9\u6837\u65e2\u51cf\u5c11\u4e86\u4e00\u884c\u4ee3\u7801\uff0c\u53c8\u907f\u514d\u4e86\u4e24\u6b21\u8c03\u7528 `some_func` \u51fd\u6570\u3002\n",
        "\n",
        "- \u5728\u9876\u5c42\u7684\u65e0\u62ec\u53f7\u8d4b\u503c\u64cd\u4f5c\uff08\u4f7f\u7528\u201c\u6d77\u8c61\u201d\u8fd0\u7b97\u7b26\uff09\u88ab\u9650\u5236\uff0c\u56e0\u6b64\u4f8b1\u4e2d\u7684 `a := \"wtf_walrus\"` \u51fa\u73b0\u4e86 `SyntaxError` \u3002\u7528\u62ec\u53f7\u62ec\u8d77\u6765\u3002\u5b83\u5c31\u80fd\u6b63\u5e38\u5de5\u4f5c\u4e86\u3002\n",
        "\n",
        "- \u4e00\u822c\u7684\uff0c\u5305\u542b `=` \u64cd\u4f5c\u7684\u8868\u8fbe\u5f0f\u662f\u4e0d\u80fd\u7528\u62ec\u53f7\u62ec\u8d77\u6765\u7684\uff0c\u56e0\u6b64 `(a, b = 6, 9)` \u4e2d\u51fa\u73b0\u4e86\u8bed\u6cd5\u9519\u8bef\u3002\n",
        "\n",
        "- \u201c\u6d77\u8c61\u201d\u8fd0\u7b97\u7b26\u7684\u8bed\u6cd5\u5f62\u5f0f\u4e3a\uff1a`NAME:= expr`\uff0c`NAME` \u662f\u4e00\u4e2a\u6709\u6548\u7684\u6807\u8bc6\u7b26\uff0c\u800c `expr` \u662f\u4e00\u4e2a\u6709\u6548\u7684\u8868\u8fbe\u5f0f\u3002 \u56e0\u6b64\uff0c\u8fd9\u610f\u5473\u7740\u5b83\u4e0d\u652f\u6301\u53ef\u8fed\u4ee3\u7684\u6253\u5305\u548c\u62c6\u5305\u3002\n",
        "\n",
        "  - `(a := 6, 9)` \u7b49\u4ef7\u4e8e `((a := 6), 9)` \uff0c\u6700\u7ec8\u5f97\u5230 `(a, 9) ` (\u5176\u4e2d `a` \u7684\u503c\u4e3a6)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> (a := 6, 9) == ((a := 6), 9)\n",
        "```\n",
        "```py\n",
        "    True\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> x = (a := 696, 9)\n",
        "    >>> x\n",
        "```\n",
        "```py\n",
        "    (696, 9)\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> x[0] is a # \u4e24\u4e2a\u53d8\u91cf\u6307\u5411\u540c\u4e00\u5185\u5b58\u7a7a\u95f4\n",
        "```\n",
        "```py\n",
        "    True\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "  - \u7c7b\u4f3c\u7684\uff0c `(a, b := 16, 19)` \u7b49\u4ef7\u4e8e `(a, (b := 16), 19)` \uff0c\u53ea\u662f\u4e00\u4e2a\u4e09\u5143\u7ec4\u3002 \n",
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "### > Wild imports/\u901a\u914d\u7b26\u5bfc\u5165\u65b9\u5f0f *\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "# File: module.py\n",
        "\n",
        "def some_weird_name_func_():\n",
        "    print(\"works!\")\n",
        "\n",
        "def _another_weird_name_func():\n",
        "    print(\"works!\")\n",
        "\n",
        "```\n",
        "```py\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "**Output**\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> from module import *\n",
        ">>> some_weird_name_func_()\n",
        "```\n",
        "```py\n",
        "\"works!\"\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        ">>> _another_weird_name_func()\n",
        "```\n",
        "```py\n",
        "Traceback (most recent call last):\n",
        "  File \"<stdin>\", line 1, in <module>\n",
        "NameError: name '_another_weird_name_func' is not defined\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "#### \ud83d\udca1 \u8bf4\u660e\n",
        "\n",
        "- \u901a\u5e38\u5efa\u8bae\u4e0d\u8981\u4f7f\u7528\u901a\u914d\u7b26\u5bfc\u5165\u3002\u7b2c\u4e00\u4e2a\u660e\u663e\u7684\u539f\u56e0\u662f\uff0c\u5728\u901a\u914d\u7b26\u5bfc\u5165\u4e2d\uff0c\u5e26\u6709\u524d\u5bfc\u4e0b\u5212\u7ebf\u7684\u540d\u79f0\u4e0d\u4f1a\u88ab\u5bfc\u5165\u3002\u8fd9\u53ef\u80fd\u4f1a\u5bfc\u81f4\u8fd0\u884c\u65f6\u51fa\u9519\u3002\n",
        "- \u5982\u679c\u6211\u4eec\u4f7f\u7528 `from ... import a, b, c` \u8bed\u6cd5\uff0c\u4e0a\u9762\u7684 `NameError` \u5c31\u4e0d\u4f1a\u53d1\u751f\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> from module import some_weird_name_func_, _another_weird_name_func\n",
        "    >>> _another_weird_name_func()\n",
        "```\n",
        "```py\n",
        "    works!\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "- \u5982\u679c\u4f60\u771f\u7684\u60f3\u4f7f\u7528\u901a\u914d\u7b26\u5bfc\u5165\uff0c\u90a3\u4e48\u4f60\u5fc5\u987b\u5728\u4f60\u7684\u6a21\u5757\u4e2d\u5b9a\u4e49\u5217\u8868`__all__`\uff0c\u5b83\u5305\u542b\u4e00\u7cfb\u5217\u516c\u5171\u5bf9\u8c61\uff0c\u5f53\u6211\u4eec\u8fdb\u884c\u901a\u914d\u7b26\u5bfc\u5165\u65f6\uff0c\u5217\u8868\u4e2d\u7684\u8fd9\u4e9b\u5bf9\u8c61\u5c06\u88ab\u5bfc\u5165\u3002\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    __all__ = ['_another_weird_name_func']\n",
        "\n",
        "    def some_weird_name_func_():\n",
        "        print(\"works!\")\n",
        "\n",
        "    def _another_weird_name_func():\n",
        "        print(\"works!\")\n",
        "```\n",
        "```py\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "    **Output**\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> _another_weird_name_func()\n",
        "```\n",
        "```py\n",
        "    \"works!\"\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "```py\n",
        "    >>> some_weird_name_func_()\n",
        "```\n",
        "```py\n",
        "    Traceback (most recent call last):\n",
        "      File \"<stdin>\", line 1, in <module>\n",
        "    NameError: name 'some_weird_name_func_' is not defined\n",
        "```\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "# Contributing/\u8d21\u732e\n",
        "\n",
        "\u6b22\u8fce\u5404\u79cd\u8865\u4e01! \u8be6\u60c5\u8bf7\u770b[CONTRIBUTING.md](https://github.com/satwikkansal/wtfpython/blob/master/CONTRIBUTING.md).(\u8bd1: \u8fd9\u662f\u7ed9\u539f\u5e93\u63d0\u8d21\u732e\u7684\u8981\u6c42\u6a21\u7248)\n",
        "\n",
        "\u4f60\u53ef\u4ee5\u901a\u8fc7\u65b0\u5efa [issue](https://github.com/satwikkansal/wtfpython/issues/new) \u6216\u8005\u5728\u4e0a [Gitter](https://gitter.im/wtfpython/Lobby) \u4e0e\u6211\u4eec\u8fdb\u884c\u8ba8\u8bba.\n",
        "\n",
        "(\u8bd1: \u5982\u679c\u4f60\u60f3\u5bf9\u8fd9\u4e2a\u7ffb\u8bd1\u9879\u76ee\u63d0\u4f9b\u5e2e\u52a9, \u8bf7\u770b[\u8fd9\u91cc](https://github.com/leisurelicht/wtfpython-cn/blob/master/CONTRIBUTING.md))\n",
        "\n",
        "# Acknowledgements/\u81f4\u8c22\n",
        "\n",
        "\u8fd9\u4e2a\u7cfb\u5217\u6700\u521d\u7684\u60f3\u6cd5\u548c\u8bbe\u8ba1\u7075\u611f\u6765\u81ea\u4e8e Denys Dovhan \u7684\u9879\u76ee [wtfjs](https://github.com/denysdovhan/wtfjs). \u793e\u533a\u7684\u5f3a\u5927\u652f\u6301\u8ba9\u5b83\u6210\u957f\u4e3a\u73b0\u5728\u7684\u6a21\u6837.\n",
        "\n",
        "#### Some nice Links!/\u4e00\u4e9b\u4e0d\u9519\u7684\u8d44\u6e90\n",
        "* https://www.youtube.com/watch?v=sH4XF6pKKmk\n",
        "* https://www.reddit.com/r/Python/comments/3cu6ej/what_are_some_wtf_things_about_python\n",
        "* https://sopython.com/wiki/Common_Gotchas_In_Python\n",
        "* https://stackoverflow.com/questions/530530/python-2-x-gotchas-and-landmines\n",
        "* https://stackoverflow.com/questions/1011431/common-pitfalls-in-python\n",
        "* https://www.python.org/doc/humor/\n",
        "* https://www.codementor.io/satwikkansal/python-practices-for-efficient-code-performance-memory-and-usability-aze6oiq65\n",
        "\n",
        "# \ud83c\udf93 License/\u8bb8\u53ef\n",
        "\n",
        "[![CC 4.0][license-image]][license-url]\n",
        "\n",
        "&copy; [Satwik Kansal](https://satwikkansal.xyz)\n",
        "\n",
        "[license-url]: http://www.wtfpl.net\n",
        "[license-image]: https://img.shields.io/badge/License-WTFPL%202.0-lightgrey.svg?style=flat-square\n",
        "\n"
      ]
    }
  ],
  "metadata": {},
  "nbformat": 4,
  "nbformat_minor": 2
}